The ZOO-Project is an open source processing platform. The ZOO-Project Web Processing Service (WPS) Server contains a Cross-Site Scripting (XSS) vulnerability in its EchoProcess service prior to commit 7a5ae1a. The vulnerability exists because the EchoProcess service directly reflects user input in its output without proper sanitization when handling complex inputs.The service accepts various input formats including XML, JSON, and SVG, and returns the content based on the requested MIME type. When processing SVG content and returning it with the image/svg+xml MIME type, the server fails to sanitize potentially malicious JavaScript in attributes like onload, allowing arbitrary JavaScript execution in the victim's browser context. This vulnerability is particularly dangerous because it exists in a service specifically designed to echo back user input, and the lack of proper sanitization in combination with SVG handling creates a reliable XSS vector. Commit 7a5ae1a contains a fix for the issue.