CVE-2025-6290 is a stored Cross-Site Scripting (XSS) vulnerability affecting the Tournament Bracket Generator plugin for WordPress, developed by blakelong. This vulnerability exists in all versions up to and including 1.0.0 of the plugin. The root cause is improper neutralization of user-supplied input during web page generation, specifically insufficient input sanitization and output escaping on attributes passed to the plugin's 'bracket' shortcode. An authenticated attacker with contributor-level permissions or higher can exploit this flaw by injecting arbitrary malicious scripts into pages that utilize the vulnerable shortcode. These scripts are stored persistently and executed in the context of any user who views the affected page, potentially leading to session hijacking, privilege escalation, or unauthorized actions performed on behalf of the victim user. The vulnerability does not require user interaction beyond visiting the infected page, and the attacker only needs contributor-level access, which is a relatively low privilege level in WordPress environments. The CVSS 3.1 base score is 6.4 (medium severity), reflecting network attack vector, low attack complexity, required privileges, no user interaction, and partial impact on confidentiality and integrity but no impact on availability. No known exploits have been reported in the wild as of the publication date (June 26, 2025). The vulnerability is classified under CWE-79, emphasizing improper input validation leading to XSS. No official patches or updates have been released yet, increasing the urgency for mitigation through alternative means.

For European organizations using WordPress websites with the Tournament Bracket Generator plugin, this vulnerability poses a significant risk to website integrity and user trust. Exploitation could allow attackers to execute arbitrary JavaScript in the browsers of site visitors or administrators, potentially leading to theft of authentication cookies, defacement, or unauthorized administrative actions. This can result in data breaches, reputational damage, and compliance violations under regulations like GDPR, especially if personal data is compromised. Since contributor-level access is sufficient for exploitation, insider threats or compromised contributor accounts can be leveraged to inject malicious payloads. The vulnerability's stored nature means the malicious script persists and affects all users accessing the infected content, amplifying the attack's reach. Although availability is not impacted, the confidentiality and integrity of user sessions and data are at risk. European organizations with public-facing WordPress sites that use this plugin for event or tournament management are particularly vulnerable, including sports clubs, educational institutions, and entertainment companies. The absence of known exploits in the wild reduces immediate risk but does not preclude targeted attacks or future exploitation once proof-of-concept code becomes available.

Immediately audit WordPress sites for the presence of the Tournament Bracket Generator plugin and identify all instances of the 'bracket' shortcode usage. Restrict contributor-level permissions to trusted users only, and review user roles to minimize the number of users with contributor or higher privileges. Implement Web Application Firewall (WAF) rules to detect and block suspicious input patterns targeting the 'bracket' shortcode parameters, focusing on script tags and event handlers. Sanitize and validate all user inputs at the application level using security-focused plugins or custom code to enforce strict input constraints before rendering. Regularly monitor website content for unauthorized script injections or unexpected changes, using automated scanning tools specialized in detecting XSS payloads. Educate content contributors about the risks of injecting untrusted content and enforce content submission policies. Prepare for patch deployment by subscribing to vendor updates and security advisories; apply official patches immediately upon release. Consider temporary removal or disabling of the Tournament Bracket Generator plugin if the risk is unacceptable and no patch is available. Enhance logging and alerting for suspicious activities related to shortcode usage and contributor account actions to enable rapid incident response.