CVE-2026-73316

XenForo before 2.3.13 contains a payment replay vulnerability in the PayPal REST payment provider that allows attackers to process the same webhook payload multiple times by exploiting a missing duplicate transaction ID check. Attackers can replay a valid webhook payload to trigger duplicate payment events, resulting in repeated subscription activations and unauthorized account upgrades.

• https://bombobombone.github.io/posts/cve-2026-73316/
• https://github.com/BomboBombone/CVE-2026-73316
• https://www.vulncheck.com/advisories/xenforo-payment-replay-via-paypal-rest-payment-provider
• https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/
• https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/