CVE-2024-3513 is a stored cross-site scripting vulnerability identified in the Ultimate Blocks – WordPress Blocks Plugin, a popular plugin used to enhance WordPress content editing with custom blocks. The vulnerability exists due to improper neutralization of input during web page generation, specifically insufficient sanitization and output escaping of the title tag parameter. This flaw allows authenticated users with contributor-level access or higher to inject arbitrary JavaScript code into pages. Because the malicious script is stored persistently in the page content, it executes automatically whenever any user accesses the infected page, potentially compromising user sessions, stealing cookies, or performing actions on behalf of users. The vulnerability affects all plugin versions up to and including 3.1.9. The CVSS 3.1 base score is 6.4, reflecting a network attack vector, low attack complexity, privileges required at the contributor level, no user interaction needed, and a scope change indicating that the vulnerability can affect other components beyond the plugin itself. Although no known exploits are currently reported in the wild, the vulnerability poses a significant risk due to the widespread use of WordPress and the plugin’s role in content management. The root cause is the failure to properly sanitize and escape user-supplied input in the title tag, a common vector for XSS attacks. This vulnerability falls under CWE-79, which covers improper neutralization of input during web page generation. Attackers exploiting this vulnerability can execute arbitrary scripts in the context of the affected website, leading to potential data theft, defacement, or further exploitation of site visitors.

The impact of CVE-2024-3513 is primarily on the confidentiality and integrity of affected WordPress sites and their users. Successful exploitation enables attackers to execute arbitrary JavaScript in the context of the vulnerable site, which can lead to session hijacking, theft of authentication cookies, redirection to malicious sites, or unauthorized actions performed on behalf of users. Since the vulnerability requires contributor-level privileges, attackers must first gain authenticated access, which may be feasible in multi-user environments or through compromised accounts. The scope change in the CVSS vector indicates that the attack can affect components beyond the plugin itself, potentially impacting the entire WordPress installation and its users. Availability impact is minimal as the vulnerability does not directly cause denial of service. Organizations running websites with multiple contributors or user-generated content are at higher risk, as attackers can leverage legitimate access to inject malicious payloads. The widespread use of WordPress globally means that many organizations, including businesses, educational institutions, and government entities, could be affected if they use the vulnerable plugin. The absence of known exploits in the wild currently reduces immediate risk but does not eliminate the potential for future attacks, especially as proof-of-concept code may be developed.

To mitigate CVE-2024-3513, organizations should take the following specific actions: 1) Immediately update the Ultimate Blocks plugin to a patched version once available; monitor vendor announcements for patches. 2) Until a patch is released, restrict contributor and higher privileges to trusted users only, minimizing the risk of malicious script injection. 3) Implement additional input validation and output escaping at the application or web server level, such as using Web Application Firewalls (WAFs) configured to detect and block XSS payloads targeting the title tag parameter. 4) Conduct regular audits of user-generated content, especially titles, to detect and remove suspicious scripts. 5) Employ Content Security Policy (CSP) headers to limit the execution of unauthorized scripts in the browser context. 6) Educate site administrators and contributors about the risks of XSS and safe content practices. 7) Monitor logs and user activity for signs of exploitation or anomalous behavior. 8) Consider disabling or replacing the plugin if immediate patching is not feasible and the risk is unacceptable. These measures go beyond generic advice by focusing on privilege management, layered defenses, and proactive monitoring tailored to the nature of this vulnerability.