CVE-2024-49593 is a stored cross-site scripting (XSS) vulnerability identified in the Advanced Custom Fields (ACF) WordPress plugin before version 6.3.9 and the Secure Custom Fields plugin before version 6.3.6.3. These plugins are widely used to enhance WordPress site functionality by allowing custom fields to be added and managed easily. The vulnerability arises specifically when an attacker uses the Field Group editor interface to edit one of the plugin's fields, injecting malicious JavaScript code that is then stored persistently within the plugin's data. When the stored payload is later rendered in the WordPress admin or potentially on the front end, it executes in the context of the victim's browser. This can lead to the theft of cookies, session tokens, or other sensitive information, compromising confidentiality. The CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:N) indicates that the attack can be launched remotely over the network without any privileges or user interaction, increasing the risk profile. However, the impact is limited to confidentiality with no direct effect on integrity or availability. While no known exploits have been reported in the wild, the vulnerability's presence in popular plugins makes it a notable risk. The vendor has provided updates to remediate the issue, and alternative update mechanisms exist for users of the free version on WP Engine. The weakness is categorized under CWE-79, which covers improper neutralization of input leading to XSS. This vulnerability underscores the importance of secure input handling in WordPress plugins, especially those that allow administrative editing of content fields.

The primary impact of CVE-2024-49593 is the compromise of confidentiality through stored XSS attacks. An attacker exploiting this vulnerability can execute arbitrary JavaScript in the context of an administrator or other privileged user accessing the Field Group editor or affected pages. This can lead to session hijacking, theft of authentication tokens, or unauthorized actions performed on behalf of the victim. Although the vulnerability does not directly affect data integrity or system availability, the loss of confidentiality can facilitate further attacks or unauthorized access. Organizations running WordPress sites with these plugins are at risk of targeted attacks, especially if administrative access is not tightly controlled. The ease of exploitation without authentication or user interaction increases the threat level for publicly accessible WordPress installations. Additionally, compromised admin sessions could lead to site defacement, malware injection, or data exfiltration. The absence of known exploits in the wild currently reduces immediate risk, but the widespread use of these plugins means the potential impact is significant if attackers develop and deploy exploit code.

1. Immediately update Advanced Custom Fields to version 6.3.9 or later and Secure Custom Fields to version 6.3.6.3 or later to apply the official patches addressing this vulnerability. 2. For users of the free ACF version on WP Engine, follow the vendor's documented alternative update mechanism to ensure timely patching. 3. Restrict access to the Field Group editor interface to trusted administrators only, using role-based access controls and IP whitelisting where possible. 4. Implement Web Application Firewall (WAF) rules to detect and block suspicious input patterns that may indicate XSS payloads targeting these plugins. 5. Conduct regular security audits and monitoring of WordPress admin activity logs to detect unusual behavior or unauthorized field edits. 6. Educate site administrators about the risks of stored XSS and encourage cautious handling of plugin field content. 7. Consider employing Content Security Policy (CSP) headers to limit the execution of unauthorized scripts in the WordPress admin area. 8. Backup WordPress sites regularly to enable quick recovery in case of compromise. These steps collectively reduce the risk of exploitation and limit potential damage from this vulnerability.