CVE-2026-82884 in All in One SEO Plugin
Summary
by MITRE • 09/02/2026
The All in One SEO WordPress plugin before 5.0.0.1 does not sanitise and escape some content stored in posts before rendering it back in the post editor, which could allow users with the contributor role and above to perform Stored Cross-Site Scripting attacks that trigger when a higher privileged user edits the post.
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Analysis
by VulDB Data Team • 09/02/2026
The vulnerability identified in All in One SEO versions prior to 5.0.0.1 represents a critical failure in input validation and output encoding mechanisms within the WordPress plugin ecosystem. This flaw specifically affects how content stored in posts is handled during rendering back into the post editor interface. The core technical deficiency lies in the absence of proper sanitization and escaping procedures for specific data fields before they are processed by the browser environment. In secure web application development, it is imperative that all user-supplied input be treated as untrusted until proven otherwise, and any output destined for an HTML context must be encoded to prevent interpretation as executable code. The failure to implement these controls creates a direct pathway for malicious actors to inject client-side scripts into the database through legitimate administrative interfaces.
This architectural weakness enables Stored Cross-Site Scripting attacks, which are classified under CWE-79 in the Common Weakness Enumeration standard. Unlike reflected XSS where payload delivery requires tricking a user into clicking a crafted link, stored XSS persists on the target server and is served to every victim who views the affected content. In this specific scenario, an attacker with contributor-level privileges or higher can embed malicious JavaScript within post metadata or content fields. Because the plugin fails to escape these values when rendering them in the editor, the script executes automatically whenever a user with elevated permissions opens the post for editing. This transforms a standard content management workflow into a vector for compromise, leveraging the trust relationship between the browser and the application domain.
The operational impact of this vulnerability is severe due to its reliance on privilege escalation through social engineering or insider threats within the WordPress role hierarchy. Contributors typically have limited capabilities compared to administrators but are often trusted enough to create substantial amounts of content. By exploiting this flaw, an attacker can achieve arbitrary code execution in the context of a privileged user's session. This allows for comprehensive account takeover, including the ability to modify site settings, install additional malicious plugins, or exfiltrate sensitive data such as database credentials and personal information stored within the CMS. The attack is particularly insidious because it does not require direct access to administrative panels but rather exploits the routine activity of reviewing or editing content by higher-privileged staff members.
From a threat intelligence perspective, this vulnerability aligns with ATT&CK technique T1059, specifically subtechnique 007 which covers JavaScript execution in web browsers. The attack chain involves initial access via low-privilege accounts, followed by persistence through stored payloads and privilege escalation when higher-level users interact with the compromised content. Defenders should recognize that vulnerabilities of this nature often stem from over-reliance on framework-provided security features without explicit validation at critical rendering points. The lack of strict output encoding means that even if input filtering is partially implemented, dynamic context changes during editor rendering can bypass those protections entirely.
Mitigation strategies must prioritize immediate patching to version 5.0.0.1 or later where these sanitization and escaping routines have been corrected. Organizations relying on this plugin should verify their deployment status immediately given the high severity of stored XSS in content management systems. In addition to updating, security teams should implement Web Application Firewalls configured with rulesets capable of detecting anomalous script injection patterns in post metadata fields. Regular audits of third-party plugins are essential to ensure that developers adhere to OWASP guidelines for input validation and output encoding. Monitoring user activity logs for unusual editing patterns by contributor-level accounts can also provide early detection indicators before a successful exploitation occurs, thereby reducing the window of exposure until patches are applied.