CVE-2024-9451 is a stored cross-site scripting vulnerability identified in the Embed PDF Viewer plugin for WordPress, affecting all versions up to and including 2.4.4. The root cause is insufficient input sanitization and output escaping of the 'height' and 'width' parameters used during web page generation. Authenticated users with Contributor-level access or higher can exploit this flaw by injecting arbitrary JavaScript code into these parameters. Because the vulnerability is stored, the malicious payload persists in the database and executes whenever any user accesses the compromised page, potentially leading to session hijacking, privilege escalation, or unauthorized actions within the WordPress environment. The vulnerability has a CVSS 3.1 base score of 6.4, reflecting medium severity, with an attack vector of network, low attack complexity, requiring privileges (Contributor or higher), no user interaction, and a scope change. No public patches or known exploits are currently available, but the risk remains significant due to the widespread use of WordPress and the plugin. The vulnerability is categorized under CWE-79, which covers improper neutralization of input leading to XSS attacks. The lack of output escaping and input validation in the plugin’s handling of parameters is the technical cause. Since contributors can inject scripts, this could be leveraged for persistent attacks affecting site visitors and administrators alike.

The impact of CVE-2024-9451 is primarily on the confidentiality and integrity of affected WordPress sites. Successful exploitation allows attackers to execute arbitrary JavaScript in the context of the vulnerable site, potentially stealing session cookies, performing actions on behalf of other users, or defacing content. This can lead to account takeover, data leakage, or further compromise of the WordPress environment. Since the vulnerability requires Contributor-level access, it limits exploitation to users who already have some privileges, but this is a common role for many site contributors and editors, increasing the attack surface. The stored nature of the XSS means that all users visiting the infected page are at risk, including administrators, which can escalate the severity of the attack. Organizations relying on the Embed PDF Viewer plugin for document display on their WordPress sites face risks of reputational damage, data breaches, and operational disruption if exploited. The absence of known exploits in the wild reduces immediate risk but does not eliminate it, especially as attackers often weaponize such vulnerabilities quickly after disclosure.

To mitigate CVE-2024-9451, organizations should first check for updates or patches from the plugin vendor and apply them promptly once available. In the absence of an official patch, administrators should restrict Contributor-level access to trusted users only and audit existing content for injected scripts. Implementing a Web Application Firewall (WAF) with rules to detect and block malicious payloads targeting the 'height' and 'width' parameters can provide interim protection. Additionally, site owners can sanitize and validate input parameters manually by customizing the plugin code or using security plugins that enforce strict input validation and output escaping. Monitoring logs for suspicious activity related to PDF viewer parameters and educating contributors on secure content practices are also recommended. Finally, consider disabling or replacing the Embed PDF Viewer plugin with a more secure alternative if immediate patching is not feasible.