CVE-2026-73628: s9y Serendipity

Medium severity, CVSS 6.1. EPSS: 0.3% chance of exploitation in the next 30 days.

Serendipity versions >= 2.3.5 and <= 2.6.0 contain a reflected cross-site scripting vulnerability in the search clean-URL route (/search/<term>). In include/functions_routing.inc.php serveSearch(), the sanitisation pipeline runs urldecode() after HTML-encoding, so a single URL-encoded HTML payload survives strip_tags() and htmlspecialchars() and is then decoded back into live HTML in the page. A crafted search link can execute arbitrary JavaScript in the victim's browser. Fixed in 2.6.1.

Affected products

• s9y Serendipity: from 2.3.5, up to and including 2.6.0

Published 2026-08-13. Last modified 2026-09-30.