The WP Flot plugin for WordPress, used to generate line charts via a shortcode, suffers from a stored cross-site scripting (XSS) vulnerability identified as CVE-2025-13906. This vulnerability arises from insufficient sanitization and escaping of user-supplied attributes within the 'linechart' shortcode, allowing authenticated users with contributor-level permissions or higher to inject arbitrary JavaScript code. When other users access pages containing the injected shortcode, the malicious scripts execute in their browsers, potentially leading to session hijacking, privilege escalation, or unauthorized actions within the WordPress environment. The vulnerability affects all versions up to and including 0.2.2. The CVSS 3.1 score of 6.4 indicates medium severity, with network attack vector, low attack complexity, and privileges required at the contributor level, but no user interaction needed. The scope is changed (S:C), meaning the vulnerability can affect resources beyond the vulnerable component. No patches or official fixes have been published yet, and no known exploits are reported in the wild. The vulnerability is classified under CWE-79, which covers improper neutralization of input during web page generation. This flaw is particularly dangerous in multi-user WordPress environments where contributors can add content but are not fully trusted. The lack of output escaping and input validation in the shortcode processing allows persistent injection of malicious payloads that execute in the context of site visitors, including administrators. This can lead to theft of cookies, credentials, or execution of unauthorized actions. The vulnerability highlights the importance of strict input validation and output encoding in WordPress plugins that accept user input for dynamic content generation.

For European organizations, this vulnerability poses a significant risk to WordPress-based websites, especially those that allow contributor-level users to add or edit content. Exploitation could lead to session hijacking, unauthorized access, or defacement, undermining user trust and potentially exposing sensitive data. Organizations in sectors such as e-commerce, government, education, and media that rely on WordPress for public-facing sites are particularly vulnerable. The stored nature of the XSS means that malicious scripts persist on the site, increasing the risk of widespread impact on site visitors and administrators. Given the medium CVSS score and the requirement for authenticated access, the threat is moderate but should not be underestimated, especially in environments with multiple contributors. Additionally, the scope change indicates that the impact can extend beyond the immediate plugin, potentially affecting the entire WordPress site and its users. The absence of known exploits in the wild provides a window for proactive mitigation, but the presence of this vulnerability in all plugin versions up to 0.2.2 means many sites could be exposed. The impact on confidentiality and integrity is moderate, with no direct availability impact reported. However, successful exploitation could facilitate further attacks that degrade availability or compromise broader system security.

1. Immediately audit WordPress sites for the presence of the WP Flot plugin and identify versions up to 0.2.2. 2. Restrict contributor-level permissions to trusted users only, minimizing the risk of malicious shortcode injection. 3. Disable or remove the 'linechart' shortcode functionality temporarily until an official patch or update is released. 4. Implement custom input validation and output escaping for any user-supplied attributes in the shortcode if plugin modification is feasible. 5. Monitor site content for suspicious shortcode usage or unexpected script injections. 6. Educate content contributors about the risks of injecting untrusted content and enforce strict content review policies. 7. Employ Web Application Firewalls (WAFs) with rules to detect and block common XSS payloads targeting the shortcode parameters. 8. Keep WordPress core and all plugins updated and subscribe to vulnerability notifications for timely patching. 9. Consider isolating or sandboxing contributor content submissions to prevent persistent script execution. 10. Conduct regular security assessments focusing on plugin vulnerabilities and user privilege management.