CVE-2026-73314 — XenForo < 2.3.13 Signature Verification Bypass via PayPal REST Webhook
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 validati…
Published: 2026-09-08 · CVSS: 8.7 · CVSS 4.0
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.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7