CVE-2008-4513 in Phorum
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in BBcode API module in Phorum 5.2.8 allows remote attackers to inject arbitrary web script or HTML via nested BBcode image tags.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 08/02/2021
The vulnerability identified as CVE-2008-4513 represents a critical cross-site scripting flaw within the BBcode API module of Phorum version 5.2.8. This security weakness stems from insufficient input validation and sanitization mechanisms that fail to properly escape or filter user-supplied content containing nested BBcode image tags. The vulnerability exists in the way the application processes and renders BBcode formatted text, specifically when handling nested image tags that contain malicious script content. Attackers can exploit this weakness by crafting specially formatted BBcode sequences that, when processed by the vulnerable application, execute arbitrary web scripts or HTML code within the context of other users' browsers. The flaw is particularly dangerous because BBcode is commonly used in forum environments where users frequently post content with embedded media, making the attack vector highly accessible and impactful.
The technical implementation of this vulnerability aligns with CWE-79, which describes cross-site scripting vulnerabilities resulting from improper handling of untrusted data in web applications. The flaw occurs in the BBcode parsing module where nested image tags are processed without adequate sanitization of the src attribute values. When the application encounters nested BBcode image tags containing malicious payloads, the parsing logic fails to properly escape or validate the embedded script content before rendering it to end users. This allows attackers to inject JavaScript code or HTML elements that execute in the victim's browser context, potentially leading to session hijacking, data theft, or further exploitation of the compromised user accounts. The vulnerability demonstrates a classic input validation failure where the application assumes that user-provided BBcode will be benign and does not properly account for the possibility of malicious content within nested tag structures.
The operational impact of CVE-2008-4513 extends beyond simple script execution, as it can enable sophisticated attack chains that leverage the forum environment for broader security compromise. Attackers can use this vulnerability to steal session cookies, redirect users to malicious sites, or even deploy browser-based malware through the compromised forum platform. The vulnerability is particularly concerning in multi-user environments where forum administrators and regular users share the same application context, as it can be used to target both groups simultaneously. The attack requires minimal technical expertise to execute, making it attractive to threat actors of varying skill levels. Additionally, the persistent nature of forum content means that successful attacks can affect multiple users over extended periods, potentially allowing attackers to maintain access to compromised systems or harvest sensitive information from unsuspecting forum participants.
Mitigation strategies for this vulnerability should focus on implementing comprehensive input sanitization and output encoding mechanisms within the BBcode processing module. Organizations should immediately upgrade to patched versions of Phorum where the vulnerability has been addressed through proper input validation and sanitization of BBcode content. The solution involves implementing strict validation of image tag attributes and ensuring that any user-provided content is properly escaped before rendering. Security measures should include the implementation of Content Security Policy headers to limit script execution, proper HTML entity encoding of user inputs, and regular security audits of third-party modules. From an ATT&CK perspective, this vulnerability maps to TA0001 (Initial Access) and TA0002 (Execution) techniques, as it enables attackers to gain initial access through malicious content and execute code within user browsers. Organizations should also implement web application firewalls and regular security testing to detect and prevent similar vulnerabilities in other forum platforms or web applications.