CVE-2003-0283 in Phorum
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in Phorum before 3.4.3 allows remote attackers to inject arbitrary web script and HTML tags via a message with a "<<" before a tag name in the (1) subject, (2) author s name, or (3) author s e-mail.
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Analysis
by VulDB Data Team • 08/20/2025
The vulnerability described in CVE-2003-0283 represents a classic cross-site scripting flaw in the Phorum web-based discussion forum software prior to version 3.4.3. This security weakness stems from inadequate input validation and sanitization mechanisms within the application's handling of user-submitted data. The vulnerability specifically manifests when malicious actors craft messages containing the sequence "<<", followed by a tag name, in critical user input fields including subject lines, author names, and author email addresses. This particular exploitation vector leverages the way the forum software processes and renders user content, creating an avenue for persistent XSS attacks that can compromise user sessions and execute malicious code within the context of the victim's browser.
The technical implementation of this vulnerability resides in the improper handling of HTML tag parsing within the Phorum application's rendering engine. When the software encounters a message containing the "<<sequence followed by a tag name, it fails to properly sanitize or escape the input before displaying it to other users. This processing flaw allows attackers to inject malicious HTML content that gets executed when other users view the affected messages. The vulnerability operates at the application layer and specifically targets the user interface rendering components that display forum content, making it particularly dangerous for collaborative environments where multiple users interact with shared content. This issue directly maps to CWE-79, which categorizes cross-site scripting vulnerabilities as weaknesses that allow attackers to inject malicious scripts into web applications viewed by other users.
The operational impact of this vulnerability extends beyond simple data theft or session hijacking, as it enables attackers to perform a wide range of malicious activities within the forum environment. Successful exploitation could allow threat actors to steal cookies, redirect users to malicious websites, deface the forum interface, or even execute arbitrary commands on behalf of the victim. The persistence of this vulnerability across multiple input fields - subject, author name, and author email - significantly increases the attack surface and makes it more difficult for administrators to mitigate. Users with higher privileges could potentially exploit this weakness to gain unauthorized access to administrative functions or modify forum content. The vulnerability's impact is particularly severe in environments where the forum serves as a central communication platform for organizations, as it could compromise the integrity of sensitive discussions and communications.
Mitigation strategies for this vulnerability require immediate implementation of input sanitization and output encoding measures within the Phorum application. The most effective approach involves implementing comprehensive HTML escaping for all user-supplied content before rendering it in the browser, particularly when the content may contain tag names or HTML sequences. Organizations should upgrade to Phorum version 3.4.3 or later, which includes proper input validation and sanitization mechanisms. Additionally, implementing Content Security Policy headers can provide an additional layer of protection against XSS attacks by restricting the sources from which scripts can be loaded. Security administrators should also consider implementing web application firewalls that can detect and block suspicious input patterns containing the specific sequences that trigger this vulnerability. This vulnerability aligns with ATT&CK technique T1566, which covers social engineering through malicious content injection, and demonstrates the critical importance of proper input validation in web application security.