Unauthenticated Reflected XSS via innerHTML in AVideo

WWBN AVideo is an open source video platform. In versions 25.0 and below, there is a reflected XSS vulnerability that allows unauthenticated attackers to execute arbitrary JavaScript in a victim's browser. User input from a URL parameter flows through PHP's json_encode() into a JavaScript function that renders it via innerHTML, bypassing encoding and achieving full script execution. The vulnerability is caused by two issues working together: unescaped user input passed to JavaScript (videoNotFound.php), and innerHTML rendering HTML tags as executable DOM (script.js). The attack can be escalated to steal session cookies, take over accounts, phish credentials via injected login forms, spread self-propagating payloads, and compromise admin accounts — all by exploiting the lack of proper input sanitization and cookie security (e.g., missing HttpOnly flag on PHPSESSID). The issue has been fixed in version 26.0.