High · CVSS 8.7CVE-2026-73314

XenForo < 2.3.13 Signature Verification Bypass via PayPal REST WebhookCVE-2026-73314

Answer in brief

CVE-2026-73314 records a High severity (CVSS 8.7) vulnerability in XenForo < 2.3.13 Signature Verification Bypass via PayPal REST Webhook. The current sources do not mark it as known exploited. The current feed maps XenForo/XenForo (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 8, 2026Updated Oct 1, 2026Source checked Oct 23, 2026First seen by HOL Sep 8, 2026Material review Oct 1, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 8.7
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 8.7. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps XenForo/XenForo (generic). Check affected ranges and fixed versions before updating.

Affected products and reported versions
Product	Affected versions	Fixed versions
cpe:2.3:a:xenforo:xenforo::::::::	Not reported	Not reported

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
XenForo/XenForogeneric	>=0 <2.3.13	2.3.13

Recommended response

Check inventory. Check lockfiles and deployed manifests for XenForo/XenForo.
Review the reported fix. Update XenForo/XenForo to 2.3.13 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 8, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Oct 1, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 8, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.