CVE-2004-1703 in Fusion News
Summary
by MITRE
Fusion News 3.6.1 allows remote attackers to add user accounts, if the administrator is logged in, via a comment that contains an img bbcode tag that calls index.php with the signup action, which is executed when the administrator s browser loads the page with the img tag.
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Analysis
by VulDB Data Team • 03/09/2025
This vulnerability exists in Fusion News version 3.6.1, a content management system that suffers from a critical security flaw involving improper input validation and privilege escalation. The vulnerability stems from the application's handling of user comments that contain malicious bbcode tags, specifically the img tag, which creates a dangerous execution path when processed by the system. When an administrator views a page containing such a comment, the img tag triggers an automatic call to index.php with the signup action parameter, effectively allowing remote attackers to register new user accounts without proper authentication or authorization.
The technical exploitation occurs through a sophisticated cross-site scripting attack vector combined with privilege abuse. The vulnerability leverages the fact that the application does not properly sanitize user input, particularly bbcode tags within comments. When an administrator's browser loads a page containing the malicious comment with the img tag, the browser automatically attempts to load the image resource, which in this case is a crafted URL pointing to index.php with the signup action. This automatic browser behavior bypasses normal authentication mechanisms and allows unauthorized account creation, effectively granting attackers persistent access to the system with the privileges of the newly created accounts.
The operational impact of this vulnerability is severe as it provides attackers with a persistent backdoor into the system. Since the vulnerability requires only that an administrator views a malicious page, it can be exploited through social engineering techniques or by embedding the malicious comment in public forums, news articles, or other content where administrators might browse. The vulnerability essentially transforms any comment submission into a potential privilege escalation vector, allowing attackers to create accounts with varying permission levels depending on the system's default user creation settings. This creates a significant risk of unauthorized access to administrative functions and potential system compromise.
From a cybersecurity perspective, this vulnerability aligns with CWE-79, which describes cross-site scripting flaws, and CWE-264, which covers permissions, privileges, and access controls. The attack pattern follows techniques described in the ATT&CK framework under T1078 for valid accounts and T1203 for exploitation for privilege escalation. The vulnerability demonstrates a classic case of insufficient input sanitization combined with improper access control validation, where the system fails to verify that the user performing the action has appropriate privileges. Organizations should implement proper input validation and output encoding for all user-generated content, particularly in comment systems. The recommended mitigations include implementing strict sanitization of bbcode and html content, disabling automatic execution of external resources in user comments, and ensuring that administrative actions require explicit authentication verification rather than relying on browser behavior for automatic execution.
The vulnerability highlights the critical importance of validating all user input and implementing proper access controls in web applications. It demonstrates how seemingly innocuous features like image embedding in comments can create significant security risks when combined with improper privilege validation. System administrators should regularly audit their applications for similar vulnerabilities and ensure that all user-generated content is properly sanitized before being processed or displayed. Additionally, implementing proper logging and monitoring of user account creation events can help detect unauthorized account additions that might indicate exploitation of this vulnerability. The attack vector also underscores the need for robust content security policies and the principle of least privilege, where even administrative users should not be automatically trusted to execute arbitrary actions based on external content.