XSS in Mailcow Mailcow-Dockerized

CVE-2026-40873

mailcow: dockerized is an open source groupware/email suite based on docker. In versions prior to 2026-03b, the Quarantine details modal injects attachment filenames into HTML without escaping, allowing arbitrary HTML/JS execution. An attacker can deliver an email with a crafted attachment name so that when an admin views the quarantine item, JavaScript executes in their browser, taking over their account. Version 2026-03b fixes the vulnerability.

Vulnerability class: XSS (Cross-Site Scripting)

EPSS: 0.003 (25.1th percentile) — read the EPSS interpretation.