Description
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
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| XenForo | XenForo | < 2.3.13 | 2.3.13 |
Public exploits
Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.
GitHub 1 repository
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BomboBombone/CVE-2026-73314 ★ 0 · Sep 8, 2026
Sanitized XenForo write-up and proof of concept for CVE-2026-73314.
Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.
References
- Vendor Advisory vendor-advisory patch
- Release Notes release-notes
- Researcher Advisory technical-description
- Researcher PoC exploit
- https://www.vulncheck.com/advisories/xenforo-signature-verification-bypass-via-paypal-rest-webhook third-party-advisory