CVE-2026-16957 in Slim SEO Plugin
Summary
by MITRE • 08/09/2026
The Slim SEO WordPress plugin before 4.9.11 does not restrict a post-meta preview feature to posts the user is allowed to edit, verifying only read access, allowing users with the Contributor role to read arbitrary post meta, including protected and private keys, of published posts they do not own, including password-protected posts and posts of non-public post types.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 08/09/2026
The Slim SEO WordPress plugin vulnerability represents a critical authorization flaw that undermines the security model of content management systems by permitting unauthorized access to sensitive metadata. This issue affects versions prior to 4.9.11 and demonstrates a fundamental failure in access control implementation where the plugin's post-meta preview functionality operates without proper permission validation. The vulnerability specifically targets users with the Contributor role, which typically should only allow reading published posts rather than accessing their underlying metadata structures.
The technical flaw lies in the plugin's insufficient verification mechanism that relies solely on read access checks instead of implementing comprehensive edit permissions. This design oversight creates a privilege escalation pathway where malicious actors can exploit the preview feature to extract confidential post meta information including protected and private keys. The vulnerability extends beyond simple metadata exposure to encompass password-protected posts and non-public post types, indicating a complete breakdown in the plugin's authorization framework.
From an operational perspective, this vulnerability poses significant risks to WordPress site security as it allows unauthorized users to gather sensitive information about content that should remain restricted. Attackers could potentially discover unpublished content, extract internal system references, or identify security configurations through exposed metadata fields. The impact is particularly severe for sites using password-protected posts or custom post types with restricted access, as these protections become effectively nullified when the preview feature is abused.
The vulnerability aligns with CWE-284 (Improper Access Control) and represents a classic example of inadequate privilege validation in web applications. It also maps to ATT&CK technique T1213.002 (Data from Information Repositories) as it enables unauthorized data extraction from content management systems. Organizations relying on Slim SEO plugin versions before 4.9.11 face increased risk of information disclosure attacks, especially in environments where contributors have access to sensitive content that should remain protected from unauthorized viewing.
Mitigation strategies include immediate upgrade to version 4.9.11 or later, which implements proper edit permission checks for the preview feature. Administrators should also review user roles and capabilities to ensure that contributors do not have unnecessary access to metadata preview functions. Additional defensive measures involve implementing network-level restrictions and monitoring for unusual access patterns in plugin usage, particularly around post-meta retrieval operations. Regular security audits of WordPress plugins should include verification of access control implementations to prevent similar authorization bypass vulnerabilities from compromising system integrity.