Xenforo

XenForo before 2.3.13 contains a signature verification logic error in the PayPal REST webhook handler that allows unauthenticated attackers to bypass payment signature validation by submitting a webhook request with an unsupported auth_algo header value. When the algorithm cannot be mapped to a supported hash function, the verification function incorrectly returns true instead of failing, causing the caller to treat the fabricated request as verified and process the payment event without a valid PayPal signature.

Published: 2026-09-08T13:17:52.339Z
Updated: 2026-10-01T15:20:34.739Z

XenForo before 2.3.13 contains an authorization flaw in the OAuth2 token endpoint that allows attackers controlling any allowlisted redirect URI to bypass redirect URI binding by submitting a different allowlisted URI than the one recorded at authorization time. Attackers can exchange an intercepted authorization code using a mismatched redirect URI to steal OAuth2 tokens from intercepted authorization flows.

Published: 2026-09-08T13:16:14.180Z
Updated: 2026-10-01T15:20:32.079Z

XenForo before 2.3.13 contains an uncontrolled recursion vulnerability in the BBCode parser that allows authenticated attackers to cause persistent denial of service by submitting a post with deeply nested BBCode tags. Attackers can craft a single malicious post with sufficient nesting depth to exceed PHP's stack limit, causing fatal errors that repeatedly terminate PHP-FPM workers for all visitors rendering the affected thread.

Published: 2026-09-08T13:20:16.081Z
Updated: 2026-10-01T15:20:39.261Z

XenForo before 2.3.13 contains a missing authorization vulnerability in the force-agreement controller that allows any ACP administrator to access and submit force-agreement forms regardless of their assigned permissions. Attackers can bypass the option permission declared in the navigation configuration to update the global policy last-updated timestamp, forcing all users to re-agree to the privacy policy or terms of service.

Published: 2026-09-08T13:19:14.546Z
Updated: 2026-10-01T15:20:37.317Z

XenForo before 2.3.13 contains a cross-site scripting vulnerability in the dynamic redirect handler that allows unauthenticated attackers to execute arbitrary JavaScript in the board origin by crafting a malicious javascript: URI that bypasses host validation. Attackers can embed the board hostname in the URI authority component and use percent-encoded newlines to evade server-side filters, causing authenticated users who perform a Follow action to execute attacker-supplied JavaScript in their browser.

Published: 2026-09-08T13:19:39.156Z
Updated: 2026-10-01T15:20:37.963Z