CVE-2026-73314: Xenforo

High severity, CVSS 7.5. EPSS: 0.7% chance of exploitation in the next 30 days.

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.

Affected products

• Xenforo Xenforo: before 2.3.13 (fixed in 2.3.13)

Published 2026-09-08. Last modified 2026-09-11.