CVE-2025-13159 is a stored cross-site scripting vulnerability classified under CWE-79 affecting the Flo Forms – Easy Drag & Drop Form Builder plugin for WordPress. The vulnerability arises because the plugin permits unauthenticated users to upload SVG files through an AJAX endpoint named `flo_form_submit` without validating the file content properly. SVG files can contain embedded JavaScript, which, when rendered in the WordPress admin interface by an administrator, executes in the context of the admin session. This execution can lead to full site compromise by allowing attackers to hijack admin sessions, inject malicious code, or pivot to other parts of the infrastructure. The vulnerability affects all plugin versions up to and including 1.0.43. The CVSS 3.1 score is 7.1 (high), reflecting network attack vector, low attack complexity, no privileges required, but user interaction needed (admin viewing the file), and impacts on confidentiality, integrity, and availability. Although no public exploits are known yet, the vulnerability's nature and ease of exploitation make it a significant risk. The flaw is particularly dangerous because it allows unauthenticated attackers to persistently store malicious scripts that execute with administrator privileges, bypassing typical authentication barriers. The lack of proper SVG content validation is the root cause, and the attack surface includes any WordPress site using this plugin with SVG upload enabled. The vulnerability was published on November 21, 2025, and no official patches or fixes have been linked yet, increasing the urgency for mitigation.

For European organizations, this vulnerability poses substantial risks to websites running WordPress with the affected Flo Forms plugin. Exploitation can lead to unauthorized administrative access, data theft, defacement, or deployment of further malware, impacting confidentiality, integrity, and availability of web assets. Organizations relying on WordPress for customer interaction, e-commerce, or internal portals could face service disruption and reputational damage. The stored XSS nature means the malicious payload persists and can affect multiple administrators or users over time. Given the unauthenticated attack vector, attackers can target organizations indiscriminately, increasing the threat surface. This is particularly critical for sectors with strict data protection regulations like GDPR, where breaches can lead to significant fines and legal consequences. Additionally, the ability to compromise administrative accounts can facilitate lateral movement within corporate networks, escalating the threat beyond the web server. The impact extends to supply chain risks if compromised sites serve as platforms for distributing malicious content or phishing campaigns targeting European users.

Immediate mitigation should include disabling SVG file uploads in the Flo Forms plugin settings or globally within WordPress if possible. Restrict access to the `flo_form_submit` AJAX endpoint by implementing authentication checks or IP whitelisting to prevent unauthenticated uploads. Administrators should avoid viewing uploaded SVG files until a patch is released. Employ web application firewalls (WAFs) with rules to detect and block malicious SVG payloads or suspicious AJAX requests targeting the plugin endpoint. Monitor logs for unusual upload activity or admin interface access patterns. Conduct an audit of all uploaded SVG files to identify and remove potentially malicious content. Update the plugin promptly once the vendor releases a patch addressing the vulnerability. Additionally, implement Content Security Policy (CSP) headers to restrict script execution contexts in the admin interface. Educate administrators about the risk of opening untrusted files and enforce the principle of least privilege for admin accounts. Regular backups and incident response plans should be reviewed to prepare for potential exploitation.