Description

XSS vulnerability in Markdown handling in Apache Allura. This issue affects Apache Allura: from 1.10.0 before 1.19.1. Users are recommended to upgrade to version 1.19.1, which fixes the issue.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "6.1",
  "pubDate": "2026-08-12T17:17:31.960Z",
  "pubdate": "2026-08-12T17:17:31.960Z",
  "executiveSummary": "A Cross-Site Scripting (XSS) vulnerability exists within the Markdown handling component of Apache Allura, specifically affecting versions from 1.10.0 prior to 1.19.1. This security flaw allows malicious actors to inject arbitrary client-side scripts, such as JavaScript, into rendered Markdown content viewed by other application users. The vulnerability impacts the integrity and confidentiality of user sessions within Apache Allura deployments, as successful exploitation enables attackers to execute scripts in the security context of a victim's browser session. Consequently, an attacker could potentially hijack user sessions, steal sensitive authentication tokens, or perform unauthorized actions on behalf of authenticated users. The risk implication is significant for collaborative environments where users frequently exchange rich text content. Exploitation relies on the application's failure to properly sanitize or neutralize malicious HTML and script constructs during the Markdown parsing and rendering process. Users and administrators of affected Apache Allura instances face these security implications until remedial actions are applied.",
  "technicalDetails": "The vulnerability resides in the Markdown parsing and rendering subsystem of Apache Allura, which is responsible for translating user-supplied Markdown text into HTML for web presentation. The root cause stems from insufficient input sanitization and improper output encoding during the processing of specialized Markdown syntax elements. When an unprivileged or authenticated user submits crafted Markdown payloads containing malicious HTML tags or javascript URIs, the vulnerable parser fails to strip or neutralize the executable content adequately. During the attack flow, the malicious payload is stored within the application backend, typically in a wiki page, ticket description, or comment thread. Upon retrieval, the application serves the unvalidated HTML output to secondary users viewing the affected resource. The victim's browser interprets the injected payload as legitimate application script content, leading to execution within the Document Object Model (DOM) of the victim's session. The affected component involves the internal Markdown rendering engine across Apache Allura versions 1.10.0 through 1.19.1. Network exposure is present wherever collaborative features utilize the vulnerable Markdown handling routines over HTTP or HTTPS protocols. Depending on the specific usage context within the platform, exploitation may be triggered simply by rendering content viewed by targeted users, potentially requiring no advanced privileges other than the ability to submit user-generated content or exploit existing publicly accessible repositories and pages. Post-exploitation impact encompasses session takeover, credential theft via keylogging or DOM manipulation, and unauthorized modifications to project artifacts depending on the victim's permission level."
}