CVE-2002-0902 in phpBB
Summary
by MITRE
Cross-site scripting vulnerability in phpBB 2.0.0 (phpBB2) allows remote attackers to execute Javascript as other phpBB users by including a http:// and a double-quote (") in the [IMG] tag, which bypasses phpBB s security check, terminates the src parameter of the resulting HTML IMG tag, and injects the script.
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Analysis
by VulDB Data Team • 09/11/2025
This cross-site scripting vulnerability in phpBB 2.0.0 represents a critical security flaw that allows remote attackers to inject malicious javascript code into web applications. The vulnerability specifically targets the image tag processing functionality within the phpBB forum software, which is widely used for community-based web discussions and user-generated content management. The flaw exists in how phpBB handles the [IMG] bbcode tag when processing user-submitted content, creating an avenue for persistent cross-site scripting attacks that can compromise user sessions and data integrity.
The technical implementation of this vulnerability exploits the improper sanitization of user input within the image tag rendering process. When a user submits content containing an [IMG] tag with a malformed src attribute that includes a http:// protocol identifier followed by a double-quote character, the security validation mechanisms fail to properly escape or filter these malicious inputs. This allows the attacker to break out of the intended src parameter of the HTML IMG tag and inject arbitrary javascript code that gets executed in the context of other users' browsers. The vulnerability is classified under CWE-79 as a failure to sanitize user input, specifically manifesting as a cross-site scripting flaw that bypasses security controls.
The operational impact of this vulnerability extends beyond simple script injection, as it enables attackers to perform session hijacking, steal cookies, redirect users to malicious sites, and potentially gain unauthorized access to user accounts. Since phpBB was widely deployed across forums, bulletin boards, and community platforms, this vulnerability could affect thousands of websites simultaneously. The attack vector is particularly dangerous because it requires no special privileges or authentication from the attacker, making it an ideal target for automated exploitation campaigns. Users who browse forums with compromised content would unknowingly execute malicious scripts in their browsers, creating persistent security risks for the entire user base.
Mitigation strategies for this vulnerability should include immediate patching of affected phpBB installations to version 2.0.1 or later, which contained the necessary security fixes. Organizations should implement comprehensive input validation and output encoding mechanisms, particularly for user-generated content that gets rendered in web browsers. The principle of least privilege should be enforced by ensuring that forum software runs with minimal necessary permissions and that user content is properly sanitized before storage or display. Security monitoring should include regular vulnerability scanning and content inspection to detect potential exploitation attempts. This vulnerability aligns with ATT&CK technique T1566.001 for initial access through malicious content and demonstrates the critical importance of proper input sanitization in web application security. Organizations should also consider implementing content security policies and web application firewalls to provide additional layers of protection against similar scripting attacks.