CVE-2021-3988: 
Python vulnerability analysis and mitigation

A Cross-site Scripting (XSS) vulnerability (CVE-2021-3988) exists in janeczku/calibre-web, specifically in the file edit_books.js. The vulnerability was discovered on November 15, 2024, affecting versions up to (excluding) 0.6.15. The vulnerability occurs when editing book properties, such as uploading a cover or a format, where user input is directly inserted into the DOM without proper sanitization (NVD, Huntr).

The vulnerability exists in the code handling the #btn-upload-cover change event within the edit_books.js file. The affected code directly inserts user input into the DOM using the .html() method without proper sanitization, allowing attackers to execute arbitrary JavaScript code. The vulnerability has a CVSS v3.1 base score of 6.1 (MEDIUM) with the vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N (NVD).

The vulnerability can lead to various attacks, with the primary risk being the potential theft of cookies and execution of arbitrary JavaScript code in the context of the user's browser session. This could allow attackers to perform actions on behalf of the victim user (Huntr).

The vulnerability has been fixed in version 0.6.15 of calibre-web. The fix involves changing the code to use .text() instead of .html() when displaying filenames, preventing the execution of malicious JavaScript code (Github Patch).