CVE-2021-24932 in Auto Featured Image Plugin
Summary
by MITRE • 12/13/2021
The Auto Featured Image (Auto Post Thumbnail) WordPress plugin before 3.9.3 does not sanitise and escape the post_id parameter before outputting back in an admin page within a JS block, leading to a Reflected Cross-Site Scripting issue.
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Analysis
by VulDB Data Team • 12/16/2021
The Auto Featured Image WordPress plugin vulnerability CVE-2021-24932 represents a critical security flaw that affects versions prior to 3.9.3, specifically targeting the plugin's handling of user input within administrative interfaces. This vulnerability resides in the plugin's failure to properly sanitise and escape the post_id parameter, creating an avenue for malicious actors to inject arbitrary JavaScript code into the admin environment. The flaw manifests when the plugin outputs the post_id parameter directly into a javascript context within admin pages, without adequate input validation or output escaping mechanisms.
The technical implementation of this vulnerability stems from improper input handling practices within the plugin's codebase, where the post_id parameter received from user requests is directly incorporated into javascript blocks without sanitisation. This reflects a classic reflected cross-site scripting vulnerability pattern where malicious input is immediately reflected back to the user's browser and executed. The vulnerability operates at the intersection of CWE-79, which addresses cross-site scripting flaws, and CWE-20, which covers input validation issues. The attack vector requires an authenticated administrator or user with sufficient privileges to view the affected admin page, making it particularly concerning for WordPress installations where administrative access is compromised.
The operational impact of this vulnerability extends beyond simple script execution, as it provides attackers with the ability to manipulate the administrative interface and potentially escalate privileges. When exploited, the reflected XSS could enable attackers to steal administrative sessions, modify plugin configurations, or inject malicious code that persists across user sessions. The vulnerability's presence in the admin interface means that successful exploitation could lead to complete compromise of the WordPress installation, particularly if the victim is an administrator with elevated privileges. The reflected nature of the vulnerability means that attackers could craft specific URLs containing malicious payloads that, when visited by an administrator, would execute the injected scripts.
Mitigation strategies for CVE-2021-24932 focus primarily on immediate plugin updates to version 3.9.3 or later, which contain the necessary sanitisation and escaping fixes. Organizations should also implement additional security measures including regular security audits of WordPress plugins, enforcement of the principle of least privilege for administrative accounts, and implementation of Content Security Policy headers to limit script execution capabilities. Network monitoring should be enhanced to detect suspicious administrative activities, and regular security training for administrators can help prevent social engineering attacks that might lead to exploitation. The vulnerability aligns with ATT&CK technique T1548.002, which covers abuse of group policy and administrative privilege, as compromised administrative sessions can lead to broader system compromise. Additionally, the remediation approach should include regular plugin vulnerability scanning and maintaining an inventory of all installed plugins to ensure timely updates and patch management across the entire WordPress ecosystem.