CVE-2025-9861 is a stored Cross-Site Scripting (XSS) vulnerability affecting the ThemeLoom Widgets plugin for WordPress, developed by livingos. This vulnerability exists in all versions up to and including 1.8.5 of the plugin. The root cause is insufficient input sanitization and output escaping on user-supplied attributes within the 'los_showposts' shortcode. Authenticated attackers with contributor-level privileges or higher can exploit this flaw by injecting arbitrary JavaScript code into pages generated by the plugin. Because the malicious script is stored persistently, it executes whenever any user accesses the compromised page, potentially leading to session hijacking, privilege escalation, or other malicious activities. The vulnerability has a CVSS 3.1 base score of 6.4, indicating a medium severity level. The attack vector is network-based (remote), requires low attack complexity, and privileges of at least contributor level, but no user interaction is needed for exploitation. The scope is changed, meaning the vulnerability affects resources beyond the initially vulnerable component. The impact affects confidentiality and integrity but not availability. No known exploits are currently reported in the wild, and no official patches have been linked yet. This vulnerability is classified under CWE-79, which relates to improper neutralization of input during web page generation, a common cause of XSS vulnerabilities.

For European organizations using WordPress sites with the ThemeLoom Widgets plugin, this vulnerability poses a significant risk to web application security. Exploitation could allow attackers to inject malicious scripts that execute in the browsers of site visitors or administrators, potentially leading to theft of authentication cookies, defacement, unauthorized actions performed on behalf of users, or distribution of malware. Given that contributor-level access is required, insider threats or compromised contributor accounts could be leveraged to exploit this vulnerability. The impact is particularly critical for organizations handling sensitive data or providing services where trust and data integrity are paramount, such as financial institutions, healthcare providers, and government agencies. Additionally, the persistent nature of stored XSS increases the risk of widespread impact across multiple users. This vulnerability could also be used as a foothold for further attacks within the network or to pivot to other systems. The lack of user interaction requirement means that once the malicious script is injected, any user visiting the affected page is at risk, increasing the potential attack surface.

European organizations should immediately audit their WordPress installations to identify the presence of the ThemeLoom Widgets plugin, especially versions up to 1.8.5. Until an official patch is released, organizations should consider disabling or uninstalling the plugin to eliminate the attack vector. Implement strict access controls to limit contributor-level privileges only to trusted users and enforce strong authentication mechanisms such as multi-factor authentication to reduce the risk of account compromise. Employ Web Application Firewalls (WAFs) with rules designed to detect and block typical XSS payloads targeting the 'los_showposts' shortcode parameters. Conduct thorough input validation and output encoding on all user-supplied data within custom themes or plugins to prevent similar vulnerabilities. Regularly monitor website logs and user activity for signs of suspicious behavior or injection attempts. Additionally, organizations should educate contributors about secure coding practices and the risks associated with plugin vulnerabilities. Once a patch becomes available, prioritize its deployment and verify the effectiveness of the fix through security testing.