GCHQ CyberChef Cross-Site Scripting Vulnerability in Base64 Offset Operation

A cross-site scripting (XSS) vulnerability has been identified in GCHQ CyberChef versions prior to 11.0.0. The issue arises in the 'Show Base64 offsets' operation, where unescaped Base64 data can be injected and executed as JavaScript. This vulnerability is made possible by the 'eval()' function in 'OutputWaiter.mjs', which executes script tags in the output.

Impact

Exploitation of this vulnerability allows for cross-site scripting, where an attacker can execute arbitrary JavaScript in the context of the user's browser.

Reproduction

To reproduce this vulnerability, use the 'Show Base64 offsets' operation with a crafted Base64 string that includes a script tag. The unescaped output will execute the injected script, demonstrating the XSS vulnerability.

Remediation

Users can update to GCHQ CyberChef version 11.0.0 or later, where this vulnerability has been fixed.