CVE-2025-71278: XenForo OAuth2 Unauthorized Scope Request

Severity: high (CVSS 8.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-04-01 · updated 2026-06-17
Weakness: CWE-863

Description

XenForo before 2.3.5 allows OAuth2 client applications to request unauthorized scopes. This affects any customer using OAuth2 clients on any version of XenForo 2.3 prior to 2.3.5, potentially allowing client applications to gain access beyond their intended authorization level.

Affected products

XenForo: from 2.3.0 before 2.3.5 — fixed in 2.3.5

How to fix

Upgrade to a fixed version: XenForo 2.3.5. Check the vendor advisory for mitigations.

References

https://www.vulncheck.com/advisories/xenforo-oauth2-unauthorized-scope-request
https://xenforo.com/community/threads/xenforo-2-3-5-includes-security-fix-add-ons-released.228812/

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