CVE-2006-1716 in MyBB
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in inc/functions_post.php in MyBB (aka MyBulletinBoard) 1.10 allows remote attackers to inject arbitrary web script or HTML via a JavaScript event in a BBCode img tag. NOTE: the email vector is already covered by CVE-2006-1625, although it might stem from the same core issue.
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Analysis
by VulDB Data Team • 04/30/2019
The vulnerability described in CVE-2006-1716 represents a critical cross-site scripting flaw within the MyBulletinBoard forum software version 1.10, specifically within the inc/functions_post.php file. This vulnerability enables remote attackers to execute malicious scripts in the context of other users' browsers through carefully crafted BBCode img tags containing JavaScript events. The flaw stems from inadequate input validation and sanitization of user-submitted content, particularly when processing image tags that may contain event handlers such as onclick, onmouseover, or other JavaScript event attributes. The vulnerability manifests when the forum software fails to properly escape or filter these event attributes, allowing attackers to inject malicious payloads that execute in the victim's browser when the content is rendered.
The technical exploitation of this vulnerability occurs through the manipulation of BBCode formatting syntax, specifically targeting the img tag implementation within the MyBB platform. When a user submits content containing a malicious img tag with embedded JavaScript events, the forum software processes this input without adequate security measures to prevent the execution of unauthorized code. This creates a persistent XSS vector where the malicious script can be stored on the server and subsequently executed whenever other users view the affected content. The vulnerability demonstrates a classic lack of proper output encoding and input sanitization, where user-provided data flows directly into HTML output without appropriate security controls to prevent script injection.
The operational impact of this vulnerability extends beyond simple script execution to potentially enable more sophisticated attacks including session hijacking, credential theft, and redirection to malicious websites. Attackers can leverage this vulnerability to steal cookies, modify forum content, or redirect users to phishing sites that mimic legitimate forum interfaces. The persistence of the vulnerability means that once exploited, malicious content remains active until manually removed by administrators, potentially affecting numerous users over extended periods. This type of vulnerability also demonstrates the importance of proper content security policies and the dangers of trusting user input without adequate sanitization measures. The vulnerability aligns with CWE-79 which specifically addresses cross-site scripting flaws and represents a common pattern in web application security where improper input validation leads to code execution vulnerabilities.
Security mitigations for this vulnerability should focus on implementing comprehensive input validation and output encoding mechanisms throughout the MyBB platform. The most effective approach involves sanitizing all user-provided content, particularly BBCode elements, by removing or escaping JavaScript event attributes before rendering content. Administrators should consider implementing content security policies that prevent the execution of inline scripts and restrict the sources from which resources can be loaded. Additionally, the forum software should be updated to versions that properly address this vulnerability, as the original MyBB 1.10 release contained fundamental security flaws that have since been remediated. The ATT&CK framework categorizes this as a code injection technique under the T1566 category, specifically related to the exploitation of web application vulnerabilities through malicious content injection, making it a critical target for defensive measures including web application firewalls and proper input validation controls.
The vulnerability highlights the broader security challenges faced by bulletin board systems and forum platforms where user-generated content processing creates numerous potential attack vectors. It demonstrates how seemingly benign features like image embedding can become security risks when proper sanitization controls are not implemented. Organizations running MyBB or similar platforms should implement regular security assessments, maintain updated software versions, and establish robust input validation procedures to prevent similar vulnerabilities from being exploited. The flaw also underscores the importance of security testing during development cycles and the need for comprehensive security training for developers working with user input processing and content rendering functionalities.