EUVD-2026-72753
GHSA-xc22-88fm-2h5f
Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Network-accessible webhook endpoint, no privileges needed beyond a prior purchase; integrity-only impact with no confidentiality or availability consequence.
Primary rating from Vendor (VulnCheck).
CVSS VectorVendor: VulnCheck
Lifecycle Timeline
2DescriptionCVE.org
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.
AnalysisAI
Unauthorized subscription upgrades in XenForo before 2.3.13 are achievable by replaying valid PayPal REST webhook payloads, because the platform performs no duplicate transaction ID check before processing incoming events. An attacker who possesses a legitimately captured webhook payload - for instance, from a prior genuine purchase - can retransmit it repeatedly to the XenForo webhook endpoint, triggering repeated subscription activations and elevating account privileges without additional payment. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires that the XenForo installation has the PayPal REST payment provider configured and enabled (non-default setup requiring admin configuration of PayPal API credentials). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N) reflects a straightforward network-accessible integrity attack with no authentication or interaction requirements. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Upgrade XenForo to version 2.3.13 or later, which introduces duplicate transaction ID deduplication in the PayPal REST webhook handler. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, verify your XenForo version and whether PayPal webhooks are enabled; audit recent subscription and webhook logs for repeated transactions from identical PayPal event IDs. …
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External POC / Exploit Code
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