CVE-2025-9855 is a stored Cross-Site Scripting (XSS) vulnerability affecting the Enhanced BibliPlug WordPress plugin developed by zuotian. This vulnerability exists in all versions up to and including 1.3.8 of the plugin. The root cause is insufficient input sanitization and output escaping on user-supplied attributes within the 'bibliplug_authors' shortcode. Authenticated users with contributor-level privileges or higher can exploit this flaw by injecting arbitrary malicious scripts into pages generated by the plugin. These scripts are then stored persistently and executed in the browsers of any users who view the infected pages, potentially leading to session hijacking, privilege escalation, or other malicious activities. The vulnerability has a CVSS v3.1 base score of 6.4, indicating a medium severity level. The attack vector is network-based (remote), requires low attack complexity, and privileges at the contributor level, but does not require user interaction. The scope is changed, meaning the vulnerability can affect resources beyond the initially compromised component. The impact affects confidentiality and integrity but not availability. No known exploits are currently reported in the wild, and no patches have been linked yet. This vulnerability is categorized under CWE-79, which is improper neutralization of input during web page generation, a common and critical web security issue. Given the widespread use of WordPress and the popularity of plugins to extend its functionality, this vulnerability poses a significant risk to websites using Enhanced BibliPlug, especially those that allow contributor-level users to add or edit content.

For European organizations, this vulnerability presents a moderate risk primarily to websites that use WordPress with the Enhanced BibliPlug plugin installed. Organizations that rely on WordPress for content management, especially those with multiple contributors or editors, are at risk of having malicious scripts injected into their web pages. This can lead to unauthorized disclosure of sensitive information (confidentiality impact) and unauthorized modification of content or user data (integrity impact). The stored nature of the XSS means that any visitor to the compromised pages can be affected, potentially leading to widespread exploitation if the site has high traffic. This could damage the organization's reputation, lead to data breaches, or facilitate further attacks such as phishing or malware distribution. The medium CVSS score reflects that while the vulnerability is exploitable remotely and easily, it requires authenticated access at contributor level, which somewhat limits the attack surface. However, in environments where contributor access is granted to many users or external collaborators, the risk increases. The vulnerability does not impact availability, so denial of service is not a concern here. Given the regulatory environment in Europe, including GDPR, exploitation leading to data leakage could have legal and financial consequences.

European organizations should take the following specific and practical steps to mitigate this vulnerability: 1) Immediately audit WordPress installations to identify the presence of the Enhanced BibliPlug plugin and verify the version in use. 2) Restrict contributor-level access to trusted users only, minimizing the number of users who can add or edit content. 3) Implement strict input validation and output encoding on all user-supplied data, especially within shortcodes and plugin-generated content. If possible, apply custom filters or security plugins that sanitize shortcode attributes. 4) Monitor website content for unexpected script injections or anomalies that may indicate exploitation attempts. 5) Since no official patch is currently linked, consider temporarily disabling the plugin or removing it until a secure version is released by the vendor. 6) Educate content contributors about the risks of injecting untrusted content and enforce secure content submission policies. 7) Employ Web Application Firewalls (WAFs) with rules to detect and block XSS payloads targeting the affected shortcode. 8) Keep WordPress core, themes, and other plugins up to date to reduce the overall attack surface. 9) Prepare incident response plans to quickly address any detected exploitation. These measures go beyond generic advice by focusing on access control, content monitoring, and temporary plugin management specific to this vulnerability.