CVE-2024-21910 is a cross-site scripting (XSS) vulnerability classified under CWE-79 that affects TinyMCE, a widely used web-based rich text editor, in versions before 5.10.0. The vulnerability arises due to improper neutralization of input during web page generation, specifically when processing image or link URLs. An unauthenticated remote attacker can craft malicious URLs that, when inserted into the editor, cause arbitrary JavaScript code to execute in the context of the editing user's browser. This can lead to theft of session tokens, user impersonation, or manipulation of the editor's content. The vulnerability requires user interaction, as the victim must load or interact with the malicious content within the editor interface. The CVSS 3.1 score of 6.1 reflects a medium severity, with attack vector network (AV:N), low attack complexity (AC:L), no privileges required (PR:N), but requiring user interaction (UI:R). The scope is changed (S:C) because the vulnerability affects components beyond the vulnerable TinyMCE instance, potentially impacting the user's session and data confidentiality and integrity. No known exploits have been reported in the wild yet. The vulnerability underscores the importance of proper input sanitization and output encoding in web applications, especially those handling rich text and user-generated content. TinyMCE 5.10.0 and later versions include patches that address this issue by improving input validation and sanitization mechanisms.

For European organizations, the impact of CVE-2024-21910 can be significant, particularly for those relying on TinyMCE in web applications that handle sensitive or confidential information. Successful exploitation could allow attackers to execute arbitrary scripts in the context of authenticated users, leading to session hijacking, data theft, or unauthorized actions performed on behalf of users. This compromises confidentiality and integrity of data but does not directly affect availability. Organizations in sectors such as finance, healthcare, government, and media, where web-based content editing is common, may face increased risks. Additionally, the vulnerability could be leveraged as a stepping stone for more sophisticated attacks, including phishing or lateral movement within networks. The requirement for user interaction limits mass exploitation but targeted attacks against high-value users remain a concern. The lack of known exploits in the wild suggests a window of opportunity for proactive mitigation before widespread abuse occurs.

To mitigate CVE-2024-21910, European organizations should prioritize upgrading TinyMCE to version 5.10.0 or later, where the vulnerability is patched. In addition, implement strict input validation and sanitization on all user-supplied content before it is processed or rendered by the editor. Employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts and reduce the impact of potential XSS attacks. Regularly audit and monitor web applications for suspicious activity related to script injection. Educate users about the risks of interacting with untrusted content within web editors. For organizations unable to immediately upgrade, consider disabling or restricting features that allow insertion of image or link URLs or applying server-side filtering to sanitize inputs. Finally, maintain an up-to-date inventory of web components and dependencies to ensure timely application of security patches.