CVE-2026-73319: XenForo cross-site scripting in dynamic redirect handler

CVE-2026-73319 · Severity: medium · CVSS 6.1 · Published 2026-09-08

XenForo is a community forum platform used to host discussion boards. A cross-site scripting vulnerability in its redirect handler allows an attacker to trick authenticated users into executing malicious JavaScript within the forum's origin by crafting a specially formatted link. When a user clicks the attacker's link and confirms a "Follow" action, arbitrary JavaScript runs with access to their session and account data.

Quick answers

Is CVE-2026-73319 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-73319 being exploited in the wild.
How severe is CVE-2026-73319?
Medium severity, with a CVSS score of 6.1, published 8 September 2026.
Which products and versions are affected?
XenForo XenForo before 2.3.13.
Is there a fix for CVE-2026-73319?
A patch was published on 2026-09-08: XenForo 2.3.13 released with fix Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-73319 attacked?
It is attacked over the network.
Am I affected by CVE-2026-73319?
Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

The vulnerability exists in XenForo's dynamic redirect validation logic, which fails to restrict URI schemes when validating same-host redirects. An attacker can craft a javascript: URI (e.g., javascript://board.example/%0Awindow.name='marker';void 0) that bypasses host validation by embedding the target hostname in the URI authority component and using percent-encoded newlines (%0A) to evade filters. The validator uses PHP's URL parser to extract the host but does not check the scheme, allowing the malicious URI to pass. When an authenticated user visits the crafted Follow confirmation link and confirms the action, the browser executes the JavaScript payload in the XenForo origin with the user's privileges. Attack requires user interaction (clicking the link and confirming) but no attacker account. XenForo 2.3.13 fixed this by restricting accepted URI schemes in the redirect handler.

Affected products

  • XenForo XenForo before 2.3.13

Timeline

  • 2026-09-08: disclosed
  • 2026-09-08: patched: XenForo 2.3.13 released with fix

References

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