Web browsers are essential for navigating the Internet, serving as gateways to online information, services, and applications. However, their ubiquity and complexity make them prime targets for cyberattacks, ranging from malware infections to sophisticated zero-day vulnerabilities.

Web browsers are the most widely used software applications for accessing the Internet. From browsing websites to running web applications, they serve as a conduit for various online activities. However, their role as entry points to the Internet makes them highly vulnerable to attacks. Web browser security encompasses measures to safeguard users and systems against malicious activities such as data breaches, phishing, cross-site scripting (XSS), cross-site request forgery (CSRF), and zero-day vulnerabilities.

With the proliferation of sophisticated cyber threats and the growing reliance on browsers for everything from online banking to remote work, securing web browsers has become a critical concern for developers, security professionals, and end-users. While some of the content here is targeted towards technical professionals and may be too technical for some, even end users who use a web browser will find some value here.

Web Browser Security and Privacy

Today’s most common web browsers include Google’s Chrome, Mozilla’s Firefox, Microsoft’s Internet Explorer and Edge, Apple’s Safari, and Opera. There are also plenty of search engines in use today, like Google, Bing, DuckDuckGo, for example. Users of each browser and search engine have a reason they prefer the one that they use from the compatibility of extensions, its speed, its dedication to security and privacy, compatibility on various operating systems (macOS, Windows, Linux, etc.), or if a free VPN is provided with the application.

Efforts have been made to make browsers more secure since the inception of the Internet. Web browser security and privacy are left to the user and the company providing the web browser. Web browser companies are responsible for implementing security features and privacy settings. Also, users can expect a certain level of protection.

Hackers exploit the existing functionality in web browsers for various malicious activities; they often use these exploits as a gateway to launch cross-site request forgery attacks and execute denial-of-service attacks. UI redress attacks, cursorjacking, and clickjacking are significant threats to web browsers. With the advancement in web technologies, browsers are becoming more sophisticated. Their main goal is to provide an excellent browsing experience to the user, and they achieve this by storing lots of information locally on the user’s computer.

Browser Storage

Browsers offers a variety of options for storing data locally on a user’s device, with varying lifetimes and capacities, allowing for better performance, offline capabilities, and personalized experiences. Each storage type is suited for different use cases.

For example, cookies are files that store small amounts of data (up to 4KB) sent with each HTTP request to the server. They are used in session management, tracking, and personalization. Local storage persistently stores key-value pairs accessible within the same origin (domain); main purpose is to store nonsensitive data like preferences, themes, etc. Session Storage is like local storage, but data is only available for the duration of the page session (until the browser tab is closed).

Using small databases like IndexedDB is another type of browser storage, designed to handle larger, more structured data storage on the client side, enabling offline apps, fast queries, and data persistence for complex web applications.

Storing data locally that can be accessed directly from the browser offers multiple advantages, such as lower bandwidth and reduced work on the server side, leading to much better personalized use of web applications. While potentially raising privacy concerns, persistent browser storage mechanisms testify to the browsers’ commitment to enhancing user experience.

Browser history and cookies stored on computers mainly contribute to user privacy. Each website sets its cookies on the user’s browser for a better experience, and browser history information is stored in a centralized location in the user’s browser settings. The machine owner is responsible for and in complete control of its privacy and browser settings; any misconfiguration in these settings on individual browsers may pave the way to attacks, such as history sniffing, cache sniffing, cookie sniffing, and cookie harvesting.

Browser Vulnerability Types

When the user interacts with the web, the request passes through various security layers that are put in place to protect the network from fetching a page onto the screen; contents delivered may be known/unknown OR trusted/untrusted, depending on which site the user is interacting with. Humans and IoT devices are always keen to connect to the Internet, and the web browser is a conduit for sending requests and receiving responses.

Operating systems are designed securely and drop any incoming networking connections from untrusted sources, making it very difficult for an attacker to gain direct access to a computer; the same is not valid for web browsers; they run code from untrusted sources whenever it’s presented with scripts. Web Browsers are widespread and are used almost daily to perform sensitive transactions, such as online purchases via credit/debit card, viewing medical history, financial transactions, etc.

Securing the browser is important as it is hackers’ common target and an attack on the browser is considered an attack on users’ privacy. In this section I will cover some of the various types of browser vulnerabilities.

Cross-site Scripting [XSS] Attack:

Cross-site scripting (XSS) attacks represent a category of injection threats in which malicious scripts are inserted into otherwise safe and trusted websites. These attacks happen when an attacker leverages a web application to deliver malicious code, typically as a client-side script, to another user. Vulnerabilities that permit these attacks are relatively common and can be found in any web application that utilizes user input in the output generated without proper validation or encoding.

There are mainly three types of Cross-site Scripting attacks, namely,

• Reflected XSS, where the attacker injects malicious script via the current HTTP request.
• Stored XSS, where the malicious script is stored in the website’s database.
• DOM-based XSS, where the vulnerability is exploited in client-side code instead of server-side code.

I am just going to show one example, using the DOM-based XSS vulnerable code model, because they are very similar: For example, consider you have the following code:

And the URL you used to get to this HTML code is not so safe. You think you are just executing a page that is safe, but if the attacker crafted a URL such as http://example.com/?uname=<script>alert('XSS')</script>, the script executes the malicious JavaScript code.

A properly created version of this code would encode that uname parameter to make sure that the script that is contained in that string cannot be treated like script using something like encodeHTML(). Now no matter what string is sent to the parameter, it will just look like a simple value and could only be treated as HTML.

Cross-site Request Forgery [CSRF] :

Cross-Site Request Forgery (CSRF) is a serious attack that allows malicious actors to perform actions on behalf of authenticated users, resulting in the unauthorized takeover of user sessions. CSRF attacks thrive on overly permissive Cross-Origin Resource Sharing (CORS) settings, which create significant security risks.

CORS is essential for ensuring that cross-origin requests (requests made from one domain to another) are securely managed. It allows developers to safely integrate third-party services, enable complex web apps, and protect users from malicious activity by specifying which domains are allowed to access resources and under what conditions. Without it, modern web apps that rely on APIs or distributed services would be vulnerable to attacks like Cross-Site Request Forgery (CSRF) or data theft.

Browsers have established vital protections, such as the Same Origin Policy (SOP), which strictly limits communication between different sites. When the Same-Origin Policy is relaxed during the development lifecycle, CORS headers can threaten and undermine an application’s security, posing far greater risks than other security headers that can enhance protection. It is most important that developers pay attention to CORS settings and configure them correctly to safeguard against CSRF vulnerabilities.

Vulnerable Code:

This creates a page that looks like the following:

How this vulnerable code works:

• Form Submission: The form is designed to send a POST request to http://xyz.com/update-profile with a user’s new email when the user clicks the “Update Email” button.
• Authentication: In this simplified example, user authentication is assumed to be handled via a session cookie (session-id).
• No CSRF Protection: There’s no mechanism to verify that the request is coming from the user intentionally. The user might be tricked into submitting this form unknowingly via a malicious website, and the request would still include the valid session cookie if the user is logged in.

Preventing CSRF is primarily the responsibility of a web developer, though users also can take several precautions, mostly by being careful the sites you are connecting to. For example, use Multi-Factor Authentication [MFA], be careful with logged-in-sessions, and always log out of sensitive websites after use (especially on shared or public computers), avoid clicking suspicious links, clear cookies and caches regularly, etc.

UI Redressing [Clickjacking]

Imagine a situation where Alice, a genuine user, is lured to a malicious website, possibly via a phishing email from Bob, promising a reward. Unbeknownst to her, the web developer has deceived her into clicking a hidden button, resulting in a payment being made on a different site. This is referred to as a UI Redressing Or a Clickjacking attack.

The technique involves embedding an invisible, interactive web page (or multiple pages) with a button or hidden link, for instance, within an iframe. This works by using an iframe strategically placed above the content Alice expected to see on the fake web page.

In contrast to a CSRF attack, this kind of attack necessitates the user to perform an action, like clicking a button, whereas a CSRF attack creates a complete request without the user’s awareness or involvement.

As a user, protecting yourself against clickjacking attacks requires some awareness and taking a few precautionary steps as below,

• Keep your browser up to date.
• Use script-blocking extensions like NoScript.
• Be cautious with unfamiliar websites and links.
• Use two-factor authentication where possible.
• Look for visual clues to identify deceptive UI.
• Rely on browsers with strong security features.

By staying vigilant and taking a few simple steps, one can significantly reduce the risk of falling victim to clickjacking.

As an example of the kind of code that can be used in a clickjacking type of attack, consider the following:

This sample code demonstrates that an attacker hosted a site with a fake [Play] button, which has an invisible iframe covering the legitimate form submission page. When the admin user clicks the Play button, it actually submits the legitimate form:

Of course, that next page you go to may look exactly like the page you expected to go to. So it never hurts to keep your eye on the URL you are going to.

Double Clickjacking

Clickjacking attacks have been around for years and can be mitigated when developers implement protections into their applications. Security researcher Paulos Yibelo reveals how malicious actors can compromise users’ credentials when users double-click in Chrome, Edge, Safari, or any web browser client.

Double clickjacking can bypass established clickjacking protections by adding another layer of attack that relies upon mouse double-click timing. It quickly tricks the victim into validating a login or some other account authorization while they believe they are clicking on something else that is on the screen at the time (Like CAPTCHA or Cloudflare humanity checking).

In a matter of moments, a new window is opened, and the user is asked to double-click on a prompt while, in the blink of an eye, the hacker is switching the context to a different window altogether. Unfortunately, no solid defence mechanism exists against timing-based attacks, though Yibelo suggests strategies to mitigate this threat:

• JavaScript security: Using scripts that limit important buttons until user actions, like mouse movements, are detected.
• HTTP headers: Implementing headers that prevent rapid context-switching between browser windows during double-clicks, complicating exploitation for attackers.

These measures help to reduce unintentional clicks on sensitive elements.

Browser Extensions:

Browser extensions are tiny programs that execute within the browser environment, enhancing functionality and enriching users’ online browsing experience. Several factors, including the installation sequence of each extension, influence the order in which they function. it’s users’ decisions, such as the relative installation times of each extension, that ultimately determine the operational sequence, making the user a key player in their browsing experience.

One important thing to note here extension installed most recently will generally operate last in the execution sequence, meaning that if a malicious extension is installed after legitimate ones, it will have the potential to modify or intercept actions taken by the earlier extensions , to give you scenario , let’s consider below ,

• User installs a legitimate ad-blocker extension first.
• Later, a malicious extension is installed that is designed to inject ads on websites.

Since the malicious extension was installed last, it will execute after the ad-blocker, effectively bypassing its functionality and displaying unwanted ads.

Many web applications add browser extensions to improve their functionality; some of these extensions are malicious and can access sensitive data without the user’s knowledge. Malicious browser extensions pose a significant security issue and have rapidly emerged as one of the most common contributors to undermining Internet safety. This trend is primarily attributed to their widespread adoption and their broad permissions.

Once installed, these harmful extensions are activated and seek to breach the browser of the targeted individual, this makes them particularly elusive and challenging to combat. Below is a screenshot of the Grammarly extension which is non-malicious and primarily used to check and improve your writing. It can be used on any website or online platform and once installed will help you by identifying and correcting grammar, spelling, punctuation, and even suggesting better word choices in real-time as you type.

However, like any extension, you have granted it some amount of access to your data and malicious or not, users should be aware of the access they have provided, and what that extension can read or change the data; the browser extension setting option provides all information.

Late last year, on Christmas Eve [December 24th, 2024] there was an attack using a compromised a Cyberhaven employee’s access to the Google Chrome Web Store. The attacker used this access to publish a malicious version of our Chrome extension (version 24.10.4). The Cyberhaven Chrome Extension attack was part of a wider campaign to target Chrome extension developers across a wide range of companies. For browsers running the compromised extension during this period, the malicious code could have exfiltrated cookies and authenticated sessions for certain targeted websites. Initial findings show the attacker was targeting logins to specific social media advertising and AI platforms.

There are multiple ways user can safeguard from malicious browser extensions, for example avoiding excessive permission, suspicious resource, one needs to download extensions from reliable source.

The Role of Web Developers in Browser Security:

Web developers play a critical role in ensuring browser security, safeguarding users’ data and privacy while maintaining websites’ integrity and functionality. In the last two decades, digital environments have become more complex, and dangers like malware, phishing, and data breaches are always looming; web developers work at the forefront to secure websites and protect users from harmful individuals.

Implementing Secure Communication (HTTPS):

Secure communication between browser and server is critical; web developers must ensure that these are encrypted using HTTPS, which prevents attackers from intercepting or tempering sensitive information such as login credentials or financial details. Developers can enforce HTTPS by setting HTTP headers that tell browsers to always use a secure website connection.

Preventing Cross-Site Scripting (XSS)

To prevent XSS attacks, developers need to ensure that user input (e.g., forms and search bars) is sanitized before being rendered on the page. This is crucial as it prevents attackers from injecting malicious scripts into a website (via XSS), which could execute in users’ browsers and steal information or perform other harmful actions. Implementing a Content Security Policy (CSP)is another way to restrict XSS attacks; developers can implement CSP headers to restrict where resources (like JavaScript or images) can be loaded. This significantly reduces the risk of such harmful actions being executed on the website.

Protecting Against Cross-Site Request Forgery (CSRF)

By using anti-CSRF tokens, developers can verify that a request made to the server is from a legitimate user action, not a malicious website. This is a significant step in preventing CSRF attacks. Similarly, setting up the SameSite attribute for cookies prevents browsers from sending cookies along with cross-site requests, further strengthening the security of their applications.

Securing Authentication and Session Management

Secure authentication and session management are key to any application development. Web developers should implement multi-factor authentication for an added layer of security; this makes it difficult to gain unauthorized access to user accounts. Developers must ensure that session cookies are securely transmitted (using the Secure and HttpOnly flags) and implement session expiration or timeout mechanisms to limit the window of opportunity for attackers. Developers must securely store user passwords using strong hashing algorithms (like bcrypt or Argon2) instead of storing them as plain text.

Protecting Against Clickjacking

To protect against Clickjacking, Developers must use the X-Frame-Options HTTP header to prevent their site from being embedded in a frame or iframe on a malicious website, reducing the risk of clickjacking attacks. Equally significant is the Content Security Policy (CSP) Frame Ancestors Directive, a best practice for Clickjacking mitigation. This directive specifies which domains can embed the website in a frame, playing a crucial role in Clickjacking prevention.

Privacy Considerations

The most critical aspect Web developers need to pay attention to is privacy consideration. A key part of this is setting up cookies with secure and HttpOnly flags, as such best practices ensure that cookies containing sensitive data are not exposed to JavaScript unless absolutely necessary, thereby protecting user privacy. Another vital point to consider is avoiding tracking by third-party scripts, which could compromise users’ anonymity.

The role of a web developer is crucial in securing the web and ensuring users can browse the Internet safely. By implementing best practices and staying up to date on the ever-evolving landscape of security threats, developers contribute directly to the resilience of the entire Internet.

Future Directions in Web Browser Security

In this section I will discuss some of the ways that security in web browser seems to be headed towards, Some of these are already emerging.

AI and Machine Learning for Threat Detection

Integrating artificial intelligence (AI) and machine learning (ML) into web browser security is a future that requires more research. Advanced technologies like AI and ML can help browsers detect anomalous behaviors, identify zero-day vulnerabilities, and predict emerging threats. AI-driven security systems always have an edge in detecting new attack patterns over traditional rule-based systems, potentially offering significantly more effective protection and reassuring us about security advancements.

Post-Quantum Cryptography

As quantum computing advances, it threatens to render current encryption algorithms vulnerable. Developing post-quantum cryptography (PQC) algorithms, which are resistant to quantum attacks, is a critical area of research for browser security. Future browsers will need to implement quantum-resistant protocols to protect data confidentiality and integrity in a post-quantum world.

Decentralized Web and Privacy

The increasing demand for privacy-focused browsing experiences and user preference validation is driving browser security innovation. Decentralized authentication, privacy-oriented browsing modes, and blockchain-based identity management are anticipated to play a more significant role in shaping the future of secure web browsing.

Conclusion

Web browser security is a complex field that requires continuous innovation to address a diverse range of threats. While current defense mechanisms such as sandboxing, HTTPS, and CSP provide significant protection, new challenges arise as cyber threats become more sophisticated, and users demand greater privacy.

Every typical user of web browsers faces the exact same issue, be them the non-technical user, or the advanced cyber security experts. The only 100% safe use of the internet is to not use the internet. Clearly this is not reasonable, but you can mitigate your risk by only using well respected, up to date browsers (and applications.) Making sure your browser requires secure connections and overriding that only when you are 100% sure of the source is very important.

Advanced technologies such as AI, quantum-resistant cryptography, and decentralized web protocols are the future for web browser security implementation, and they look promising, although significant challenges remain. It’s clear that the only way to overcome these challenges is through collaboration. Researchers, developers, and security professionals must unite in their efforts to ensure that web browsers remain safe, reliable, and user-friendly in the years to come.

References

1. Google. (2020). “Securing Chrome: Architecture and security features.” Google Developer Blog.
2. Zhou, Y., & Zeng, X. (2021). “The Evolution of Cross-Site Scripting Attacks and Countermeasures.” Journal of Computer Security.
3. Rescorla, E. (2018). “HTTP Strict Transport Security (HSTS).” RFC 6797.
4. Mozilla. (2023). “Firefox Security Features.” Mozilla Developer Network.
5. Al-Sarem, M., & Wang, X. (2020). “Machine Learning-Based Approaches for Web Browser Security.” International Journal of Cybersecurity.
6. Pablo Picazo-Sanchez, Juan Tapiador & Gerardo Schneider. “After you, please: browser extensions order attacks and countermeasures.” International Journal of Information Security.