CVE-2025-9850 in Evenium Plugin
Summary
by MITRE • 09/11/2025
The Evenium plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the plugin's 'evenium_single_event' shortcode in all versions up to, and including, 1.3.11 due to insufficient input sanitization and output escaping on user supplied attributes. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.
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Analysis
by VulDB Data Team • 09/11/2025
The CVE-2025-9850 vulnerability affects the Evenium plugin for WordPress, a popular event management solution that allows users to create and display event information on their websites. This particular flaw represents a critical security weakness that undermines the integrity of WordPress installations using this plugin, particularly when exploited by malicious actors with contributor-level privileges or higher. The vulnerability exists within the plugin's 'evenium_single_event' shortcode implementation, which processes user-supplied attributes without adequate sanitization measures. The flaw demonstrates a classic stored cross-site scripting vulnerability that enables attackers to inject malicious scripts into the plugin's output, creating persistent security risks for all website visitors.
The technical root cause of this vulnerability stems from insufficient input validation and output escaping mechanisms within the plugin's shortcode processing logic. When users with contributor-level access or higher create or edit posts containing the 'evenium_single_event' shortcode, they can inject malicious attributes that are not properly sanitized before being rendered in the final HTML output. This failure to implement proper input sanitization means that attacker-controlled data can be directly embedded into the web page structure without adequate protection measures. The vulnerability specifically affects all versions of the plugin up to and including version 1.3.11, indicating that this security gap has persisted for an extended period without proper remediation. This represents a clear violation of secure coding practices and demonstrates the importance of implementing comprehensive input validation and output escaping mechanisms.
The operational impact of this vulnerability is significant for WordPress website administrators and their users. Attackers with contributor-level access can exploit this weakness to inject malicious scripts that will execute whenever any user accesses a page containing the compromised shortcode. This creates a persistent threat vector that can be used to steal user credentials, deface websites, redirect visitors to malicious sites, or perform other malicious activities. The vulnerability affects the entire user base of affected WordPress installations, as any visitor who accesses a page containing the compromised shortcode becomes a potential victim of the stored XSS attack. This makes the vulnerability particularly dangerous in environments where multiple users have contributor-level access or higher, as it provides a persistent backdoor for attackers to maintain access and conduct further exploitation activities.
Organizations and WordPress administrators should immediately implement mitigations to address this vulnerability. The primary recommendation is to upgrade to the latest version of the Evenium plugin where the XSS vulnerability has been patched and properly addressed. Until such an upgrade is possible, administrators should consider restricting contributor-level access to only trusted individuals and implementing additional monitoring of user-generated content containing shortcodes. The vulnerability aligns with CWE-79, which describes cross-site scripting flaws, and represents a clear violation of the principle of least privilege and secure input handling. From an ATT&CK perspective, this vulnerability enables techniques such as credential theft through web session hijacking and persistent threat maintenance, as the stored nature of the XSS allows attackers to maintain access over extended periods without requiring repeated exploitation attempts. Security teams should also consider implementing content security policies and regular security audits of installed plugins to identify similar vulnerabilities that may exist in other third-party components.