High

Unauthorized OAuth2 Scope Request in XenForo before 2.3.5

IdentifiersCVE-2025-71278CWE-863· Incorrect Authorization

CVE-2025-71278 is an authorization flaw in XenForo 2.3 prior to 2.3.5 affecting OAuth2 client applications. According to the provided content, vulnerable XenForo versions allow OAuth2 clients to request scopes they should not be permitted to obtain. As a result, the authorization process can grant client applications access beyond their intended authorization level. The issue affects customers using OAuth2 clients on any XenForo 2.3 release before 2.3.5.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation can allow an OAuth2 client application with low-privilege access to obtain unauthorized scopes and thereby gain access to resources or capabilities beyond those intended by the authorization model. Based on the provided CVSS vectors and description, this may result in significant confidentiality, integrity, and availability impact depending on what protected actions or data are exposed through the improperly granted scopes.

Mitigation

If you can’t patch tonight, do this now.

If immediate upgrade is not possible, limit or disable use of OAuth2 client applications where feasible, restrict registration and approval of OAuth2 clients to trusted applications only, and review authorization policies and issued tokens for excessive scopes. Monitor for OAuth2 clients requesting or using scopes beyond their expected role until the platform can be updated. Specific vendor-provided workaround details are not available in the provided content.

Remediation

Patch, then assume compromise.

Upgrade XenForo to version 2.3.5 or later, as the provided content states that XenForo 2.3.5 includes the security fix for this issue. Review existing OAuth2 client configurations and granted scopes to ensure no client has retained excessive permissions that were improperly obtainable prior to the fix.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType

XenforoXenforoapplication

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

5 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

5 SOURCESView more in app

cvefeed high severityNews

Apr 1, 2026

CVE-2025-71278 - XenForo OAuth2 Unauthorized Scope Request

An authorization flaw in XenForo before version 2.3.5 allows OAuth2 client applications to request unauthorized scopes, potentially granting access beyond intended authorization levels.

What this page doesn’t show

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Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity4