Everything you need to know about Cross-site Scripting and Sensitive Cookie Exposures

by Zill Davis Civil Lawyer

JavaScript is undoubtedly one of the most popularly used programming languages preferred by developers globally. However, security is not its strongest suit. JavaScript happens to be fourth in the list of the most vulnerable languages right after Java, C, and PHP. Hence, it is extremely important for developers to pay keen attention to JavaScript security when developing and maintaining apps using this language.

The Two Most Common Threats to JavaScript Security

Every coding language has its very own issues. If you are using JavaScript to develop an app then there are certain security threats that you should be aware of and how to deal with them. In the following section, we discuss cross-site scripting and sensitive cookie exposures and how to deal with them in detail:

Cross-Site Scripting (XSS)

Cross-site scripting falls under the client-side security threat and has been ranked as one of the most dangerous threats. Also, it was found that around 40% of all cyberattacks are XSS attacks. It occurs when the attacker injects a malicious script into the victim’s web browser by using an authentic web application. They can use both JavaScript and HTML to trigger the malicious code. This gets reinforced even more as the victim uses the web page and/or the application.

Some of these vulnerable vehicles are forums, message boards and web pages. These seem to be used quite widely to spread XSS. An attacker can exploit the vulnerabilities of XSS and make them work in tampering with data, stealing accounts and even the distribution of malware. XSS is a highly rated vulnerability as attackers can gain access to LocalStorage, SessionStorage as well as cookies.

Preventing XSS Attacks

Preventing XSS attacks is crucial for the security of the user and to do this, the developer needs to differentiate the untrusted data and the inputs from the user from within the active browser content. Some ways to do this are:

1) Validation

Validating the user’s input beforehand is advisable. This can be done by ensuring the input contains acceptable characters which are safe from XSS attacks.

2) Appropriate Frameworks

Frameworks with advanced packages contain XSS filters that are immune to XSS attacks. Using these frameworks would ensure safety against threats.

3) Encryption

The user’s input can be encrypted using sources such as HTML escape, URL escape, JavaScript escape, CSS escape, etc. Avoiding pre-existing libraries for the purpose of escaping as well as creating new libraries is recommended.

Sensitive Cookie Exposures

Server content can be accessed through client-side scripts, and these might include sensitive data such as session IDs. When session identifiers are exposed through URLs, error messages or logs, they open up the application to a number of vulnerabilities such as session fixation and session hijacking.

Preventing Sensitive Cookie Exposures Attacks

1)    1) Cookie accesses

Avoid unauthorized access to cookies by using HTTPS and HTTP-only cookies. This notifies the browser to prevent unauthorized cookie access through the DOM.

2)     2) User Authentication Requests

In order to secure user sessions, opt for per-requests instead of per-session identifiers. If and when the client requests privileged access, the current session can terminate immediately and the requester would need to re-authenticate.

3)     2) Content Security Policy

Defining the content security policy is important as it can allow the developer to define styles, fonts, frames, media, etc. Content security policy is a header and can be set using the Nginx configuration.


JavaScript security attacks can be curbed by using good coding practices to secure applications against malware attacks. Developers need to use the right methodologies for encoding, set secure cookies, use updated frameworks and libraries and can even look into React Native security for enhanced safety against attackers. 

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About Zill Davis Advanced   Civil Lawyer

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Joined APSense since, April 17th, 2021, From Los angeles, United States.

Created on Mar 9th 2022 23:14. Viewed 155 times.


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