CVE-2025-11883 is a stored Cross-Site Scripting (XSS) vulnerability identified in the Responsive Progress Bar plugin for WordPress, developed by rene-puchinger. The vulnerability exists in versions less than or equal to 1.0, where the plugin fails to properly sanitize and escape user-supplied input passed through the rprogress shortcode attributes. This improper neutralization of input (CWE-79) allows an authenticated attacker with contributor-level or higher privileges to inject arbitrary JavaScript code into pages or posts. Because the malicious script is stored in the WordPress database, it executes whenever any user accesses the affected page, potentially compromising user sessions, stealing cookies, or performing actions on behalf of the victim. The vulnerability has a CVSS v3.1 base score of 6.4, indicating medium severity, with an attack vector of network, low attack complexity, requiring privileges, no user interaction, and a scope change. Although no public exploits are currently known, the vulnerability poses a significant risk to WordPress sites using this plugin, especially those allowing multiple contributors. The lack of patch links suggests that a fix may not yet be available, emphasizing the need for immediate mitigation. The vulnerability’s impact is primarily on confidentiality and integrity, with no direct availability impact. The stored nature of the XSS increases the risk as it can affect multiple users over time.

For European organizations, this vulnerability can lead to unauthorized access to user sessions, theft of sensitive information, and potential defacement or manipulation of website content. Organizations relying on WordPress sites with multiple contributors are particularly at risk, as attackers only need contributor-level access to exploit the flaw. This can result in reputational damage, loss of customer trust, and potential regulatory non-compliance under GDPR if personal data is compromised. The vulnerability could also be leveraged as a foothold for further attacks within the organization's network or to distribute malware to site visitors. Given the widespread use of WordPress across Europe, especially among SMEs and public sector entities, the impact could be significant if exploited at scale. The absence of known exploits currently reduces immediate risk but does not eliminate the threat, as attackers may develop exploits once the vulnerability becomes widely known.

European organizations should immediately audit their WordPress installations to identify the presence of the Responsive Progress Bar plugin, especially versions ≤ 1.0. If the plugin is in use, restrict contributor-level access to trusted users only until a patch is available. Implement Web Application Firewall (WAF) rules to detect and block suspicious shortcode attribute inputs that may contain script tags or event handlers. Employ Content Security Policy (CSP) headers to limit the execution of unauthorized scripts on affected sites. Regularly monitor logs and user activity for signs of exploitation attempts. Consider disabling or removing the plugin if it is not essential to reduce the attack surface. Engage with the plugin vendor or community to obtain or develop patches and apply them promptly once released. Additionally, educate contributors on secure content practices to minimize injection risks. For critical sites, conduct penetration testing focusing on XSS vectors related to shortcodes.