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What is Blind XSS (Cross-Site Scripting)
Cross-site scripting (XSS) attacks are a form of online vulnerability that allows attackers to inject malicious code into websites. Blind XSS attacks arise when an attacker cannot see the impact of their payload but is still able to execute it on the victim’s browser. PDF and SVG files are two popular web file formats that can both contain executable code in the form of JavaScript. As a result, they are vulnerable to XSS attacks. In this post, we’ll look at whether it’s possible to embed blind XSS payloads in PDF or SVG files such that they run when opened.
To inject blind XSS payloads into PDF or SVG files, attackers can use tools like Burp Suite or ZAP to intercept the HTTP request and modify the file contents before it is delivered to the user’s browser. The attacker can introduce their XSS payload into the file in this manner, which will be executed when the file is opened.
File format attacks are another way to put XSS payloads into PDF or SVG files. These exploits can take advantage of flaws in the user’s browser or PDF viewer to execute arbitrary code. For example, in 2019, a vulnerability in Adobe Acrobat Reader was disclosed that let an attacker execute arbitrary code by inserting a specially crafted JavaScript file in a PDF file. Similarly, in 2016, a vulnerability in some versions of Firefox was uncovered that allowed an attacker to execute JavaScript code encoded in an SVG file.
It is crucial to note that vendors have corrected file format exploits, and employing them as an attack vector is not encouraged. Furthermore, by keeping software up to date with security patches and using security tools to detect and prevent XSS attacks, these types of attacks can be mitigated.
Blind XSS Payload
While blind XSS payloads can be inserted into PDF and SVG files, this is not a reliable or recommended method of attack. Exploits and vulnerabilities in these file formats can be identified and patched, so it is critical to remain aware and follow proper web security practices. Updating software, using strong passwords, and staying current on security developments and practices can all assist to prevent XSS attacks and other forms of web vulnerabilities.
Blind XSS Tool
The reference to the GitHub Gist is a proof of concept for exploiting an SVG file format vulnerability in Firefox that was discovered in 2016. While the gist demonstrates the vulnerability, it is important to note that this exploit has been patched in later versions of Firefox.
Here is the reference to the GitHub Gist:
Ioribrn. (2016). Blind XSS via SVG [GitHub Gist]. Retrieved from https://gist.github.com/ioribrn/aafd49c7c3a5cc7e1ba4848b75a52f4b
It is important to note that using this exploit on any system without explicit permission from the owner is considered unethical and illegal.
Finally, web security is a never-ending war against attackers who are continuously looking for new ways to exploit weaknesses in web technology. Blind XSS assaults are only one of the many threats that web users encounter on a daily basis. Users can assist keep attackers at bay by keeping aware and taking proactive efforts to secure themselves and their online apps.