CVE-2025-11829 is a stored cross-site scripting (XSS) vulnerability identified in the Five9 Live Chat plugin for WordPress, affecting all versions up to and including 1.1.2. The vulnerability stems from improper neutralization of input during web page generation, specifically insufficient sanitization and escaping of the 'toolbar' attribute within the [five9-chat] shortcode. This flaw allows authenticated users with contributor-level permissions or higher to inject arbitrary JavaScript code into pages or posts. When other users access these pages, the malicious scripts execute in their browsers, potentially leading to session hijacking, credential theft, or unauthorized actions performed on behalf of the victim. 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 above), no user interaction, and scope change due to impact on other components. Although no known exploits are currently reported in the wild, the vulnerability poses a significant risk in environments where multiple users have editing privileges. The flaw is categorized under CWE-79, which relates to improper neutralization of input during web page generation, a common vector for XSS attacks. The lack of patches at the time of reporting necessitates immediate mitigation steps to reduce risk.

For European organizations, this vulnerability can lead to compromise of user sessions, theft of sensitive information, and unauthorized actions performed on behalf of legitimate users, undermining confidentiality and integrity of data. Organizations relying on WordPress sites with the Five9 Live Chat plugin, especially those with multiple contributors or editors, are at heightened risk. Attackers with contributor access can embed malicious scripts that execute in the context of other users, including administrators, potentially leading to privilege escalation or data leakage. While availability is not directly impacted, the reputational damage and potential regulatory consequences (e.g., GDPR violations due to data breaches) can be significant. The medium CVSS score reflects that exploitation requires authenticated access, limiting exposure to internal or trusted users, but the scope change indicates that the impact extends beyond the initial attacker. European companies in sectors such as finance, healthcare, and e-commerce, which often use WordPress for customer engagement and support, may face increased risks from this vulnerability.

1. Immediately audit and restrict contributor-level access on WordPress sites using the Five9 Live Chat plugin to trusted personnel only. 2. Monitor and review all content using the [five9-chat] shortcode, especially the 'toolbar' attribute, for suspicious or unauthorized modifications. 3. Implement Web Application Firewall (WAF) rules to detect and block malicious script injections targeting the shortcode parameters. 4. Encourage site administrators to disable or remove the Five9 Live Chat plugin if it is not essential until a patch is released. 5. Stay alert for official patches or updates from Five9 and apply them promptly once available. 6. Educate content contributors about the risks of injecting untrusted content and enforce strict content validation policies. 7. Use security plugins that can detect and sanitize XSS payloads in WordPress content. 8. Conduct regular security assessments and penetration tests focusing on user-generated content and shortcode usage. These measures go beyond generic advice by focusing on access control, shortcode monitoring, and proactive content validation specific to this vulnerability.