Vulnerability · Published Sep 8, 2026 · Assigned by VulnCheck

CVE-2026-73316XenForo < 2.3.13 Payment Replay via PayPal REST Payment Provider

High 7.5

In plain English

A high-severity insufficient verification of data authenticity in XenForo from XenForo. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 18% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code.

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.3%top 81.5% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack tooling1Public PoC

Official description

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.

Affected products (as reported)

Vendor	Product	Versions
XenForo	XenForo	0 – before 2.3.13

Weakness: CWE-345 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

References

Vendor Advisory vendor-advisory, patch
Release Notes release-notes
Researcher Advisory technical-description
Researcher PoC exploit
https://www.vulncheck.com/advisories/xenforo-payment-replay-via-paypal-rest-payment-provider third-party-advisory