CVE-2026-73314
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 Sep 8, 2026
- CVSS 8.7 high
- 0.7% chance of exploitation in the next 30 days (EPSS)
- Public exploit code is available
- A fix is available