CVE-2025-10493 is a medium-severity vulnerability affecting the Chained Quiz plugin for WordPress, specifically versions 1.3.4 and below. The vulnerability is classified as an Insecure Direct Object Reference (IDOR), identified under CWE-639, which arises due to insufficient validation of a user-controlled key in the quiz submission and completion mechanisms. The key in question is the chained_completion_id cookie, which is used to track quiz attempts. Because the plugin fails to properly validate this cookie, an unauthenticated attacker can manipulate it to hijack and modify other users' quiz attempts. This manipulation allows the attacker to alter quiz answers, scores, and results arbitrarily. The vulnerability does not require authentication or user interaction and can be exploited remotely over the network with low complexity. Although the confidentiality impact is minimal (no direct data disclosure), the integrity of quiz data is compromised, potentially undermining the trustworthiness of quiz results and any dependent processes such as certification or assessment. The availability impact is negligible. Partial patches were introduced in versions 1.3.4 and 1.3.5, but the vulnerability remains in versions at or below 1.3.4, and no complete patch link is provided. There are no known exploits in the wild at this time. The CVSS v3.1 base score is 5.3, reflecting a medium severity level, with attack vector network, low attack complexity, no privileges required, no user interaction, and unchanged scope. This vulnerability highlights the risks of improper access control and validation in web applications, especially in plugins widely used in content management systems like WordPress.

For European organizations using the Chained Quiz plugin on WordPress sites, this vulnerability can lead to unauthorized manipulation of quiz data, which may have several consequences. Educational institutions, certification bodies, and training providers relying on these quizzes for assessments could face integrity issues, undermining the validity of their evaluations. This could result in reputational damage and loss of trust among students and clients. In sectors where quiz results influence compliance or regulatory reporting, such manipulation could have legal or financial repercussions. Additionally, attackers could leverage this vulnerability to disrupt user experience or conduct targeted misinformation campaigns by altering quiz outcomes. Although the vulnerability does not expose sensitive personal data directly, the integrity compromise could indirectly affect confidentiality if quiz results are linked to user profiles or credentials. The lack of authentication requirement increases the risk of widespread exploitation if the plugin is widely deployed. Given WordPress's popularity in Europe, especially among SMEs and educational organizations, the impact could be significant if unpatched.

European organizations should immediately verify if their WordPress installations use the Chained Quiz plugin and identify the version in use. Upgrading to the latest plugin version beyond 1.3.5, where the vulnerability is fully patched, is critical. If an upgrade is not immediately possible, organizations should implement web application firewall (WAF) rules to detect and block suspicious manipulation of the chained_completion_id cookie, such as unexpected changes or values originating from untrusted sources. Additionally, administrators should audit quiz data for anomalies indicating tampering. Implementing strict cookie validation and session management at the application level can reduce risk. Organizations should also restrict access to quiz management interfaces and monitor logs for unusual activity patterns. Educating users and administrators about this vulnerability and encouraging prompt patching is essential. Finally, consider isolating quiz functionality or using alternative, well-maintained quiz plugins with robust security practices.