CVE-2025-15549 in FluentCMS
Summary
by MITRE • 01/29/2026
FluentCMS 2026 contains a stored cross-site scripting vulnerability that allows authenticated administrators to upload SVG files with embedded JavaScript via the File Management module. Attackers can upload malicious SVG files that execute JavaScript in the browser of any user accessing the uploaded file URL.
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Analysis
by VulDB Data Team • 05/12/2026
The vulnerability identified as CVE-2025-15549 resides within FluentCMS 2026's File Management module, representing a critical stored cross-site scripting flaw that fundamentally undermines the platform's security posture. This vulnerability specifically targets the SVG file upload functionality, which is commonly used for graphical content management and asset handling. The flaw allows authenticated administrators to bypass normal file validation mechanisms and upload malicious SVG files containing embedded JavaScript code, creating a persistent threat vector that can affect all users interacting with the platform.
The technical implementation of this vulnerability stems from inadequate input sanitization and content validation within the file upload processing pipeline. When administrators upload SVG files through the management interface, the system fails to properly validate or sanitize the file contents, particularly regarding embedded script tags or JavaScript execution contexts. This weakness creates a path for attackers who can leverage their administrative privileges to inject malicious code directly into the content management system's asset repository. The vulnerability manifests as a stored XSS issue because the malicious SVG files remain persistent within the system's file storage and execute JavaScript whenever any user accesses the file URL through the web interface.
The operational impact of this vulnerability extends far beyond simple code execution, as it provides attackers with a powerful attack surface that can compromise user sessions and facilitate further exploitation. Any user who accesses the malicious SVG file URL becomes a potential victim of the embedded JavaScript payload, which can execute in the victim's browser context with the privileges of the logged-in user. This creates opportunities for session hijacking, credential theft, data exfiltration, and potential lateral movement within the compromised environment. The stored nature of the vulnerability means that the malicious code persists indefinitely until manually removed, making it particularly dangerous for long-term compromise scenarios.
Organizations utilizing FluentCMS 2026 face significant risk exposure from this vulnerability, as it requires minimal privilege escalation to exploit and can affect any user with access to the file management module. The vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws, and represents a clear violation of secure coding practices for input validation and output encoding. From an ATT&CK framework perspective, this vulnerability maps to T1566.001 (Phishing with Malicious File) and T1059.007 (Command and Scripting Interpreter: JavaScript) as attackers can leverage it to establish persistent access through malicious file uploads. The attack vector requires authentication, making it particularly concerning for organizations where administrative privileges are not adequately protected or monitored.
Mitigation strategies for CVE-2025-15549 must address both immediate remediation and long-term security hardening measures. Organizations should immediately apply the vendor-provided patch or upgrade to a patched version of FluentCMS 2026 that implements proper SVG content validation and sanitization. The recommended approach includes implementing strict file type validation, removing or disabling JavaScript execution within SVG files, and implementing Content Security Policy headers to prevent unauthorized script execution. Additionally, organizations should enforce principle of least privilege for file management operations and implement monitoring for unusual file upload activities. Network segmentation and web application firewalls can provide additional defense-in-depth layers to detect and prevent exploitation attempts, while regular security assessments should verify that proper input validation mechanisms are in place to prevent similar vulnerabilities from emerging in other components of the system.