A vulnerability exists in Apache Allura that allows a stored cross‑site scripting (XSS) flaw through the markdown HTML processing feature. Malicious input can be embedded in markdown that is then rendered as executable HTML, persisting in the database until viewed by another user. Attackers can use this to inject scripts that steal session cookies, perform phishing, or perform other client‑side attacks against users who view the compromised content.

The issue affects Apache Allura installations from the initial release up to and including version 1.20.0, made available by the Apache Software Foundation. All users operating these versions are potentially exposed unless patches are applied.

The vulnerability is a stored XSS in Apache Allura that manifests when user‑supplied markdown content containing HTML is rendered. The CVSS score of 6.1 and an EPSS score of less than 1% indicate a moderate severity with a very low probability of active exploitation; the vulnerability is not listed in CISA KEV. Based on the description, it is inferred that any user who can submit markdown content has the potential to trigger the vulnerability, which then affects other users who view the compromised content. When triggered, the impact is confined to the browsers of those users, enabling attackers to steal session cookies or perform phishing within those sessions.