CVE-2015-2333 in MyBB
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the MyCode editor in MyBB (aka MyBulletinBoard) before 1.8.4 allows remote attackers to inject arbitrary web script or HTML via unspecified vectors.
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Analysis
by VulDB Data Team • 01/10/2018
The CVE-2015-2333 vulnerability represents a critical cross-site scripting flaw within the MyCode editor component of MyBB versions prior to 1.8.4. This vulnerability exists within the forum software's text processing functionality where user input is not properly sanitized before being rendered in web pages. The vulnerability stems from insufficient validation and sanitization of user-provided content that is processed through the MyCode parser, which is designed to convert simple text formatting into HTML markup. Attackers can exploit this weakness by crafting malicious input that contains embedded scripts or HTML elements, which are then executed in the context of other users' browsers when they view the affected content. The vulnerability affects the core functionality of the forum software's content rendering system, making it a significant security concern for any deployment using vulnerable versions of MyBB.
The technical implementation of this vulnerability involves the MyCode editor's failure to adequately filter or escape special characters and script tags in user-submitted content. When users create posts or messages containing malicious payloads, the MyCode parser processes these inputs without proper sanitization, allowing attackers to inject executable code that can be interpreted by web browsers. The unspecified vectors suggest that the vulnerability can be triggered through various input points within the MyCode functionality, including but not limited to post creation, private messaging, or user profile fields. This weakness directly maps to CWE-79, which defines Cross-Site Scripting as a common web application vulnerability where untrusted data is embedded into web pages viewed by other users. The vulnerability's impact is amplified by the widespread use of MyBB in online communities, bulletin boards, and forums where user-generated content is prevalent.
The operational impact of this vulnerability extends beyond simple script execution, as it can enable attackers to perform various malicious activities including session hijacking, credential theft, and defacement of forum content. When successful, the XSS attack allows threat actors to execute arbitrary scripts in the context of other users' browsers, potentially stealing cookies, session tokens, or personal information. The vulnerability also enables attackers to modify forum content, inject phishing pages, or redirect users to malicious websites. In a typical exploitation scenario, an attacker would create a post containing malicious JavaScript code within the MyCode formatting, which would then be executed whenever other users view the post. This creates a persistent threat that can affect multiple users over time, making it particularly dangerous in community-driven platforms where content is frequently shared and viewed by many users.
The mitigation strategies for CVE-2015-2333 primarily involve upgrading to MyBB version 1.8.4 or later, which includes proper input sanitization and output encoding mechanisms. Organizations should also implement additional defensive measures such as content security policies, regular security audits of user-generated content, and input validation at multiple layers of the application. The vulnerability demonstrates the importance of proper input validation and output encoding as outlined in the OWASP Top Ten security principles, particularly focusing on the prevention of XSS attacks through proper sanitization of user inputs. Security teams should also consider implementing web application firewalls and monitoring for suspicious content patterns that may indicate attempted XSS exploitation. The remediation process should include thorough testing of the patched version to ensure that legitimate MyCode functionality remains intact while the security vulnerability is properly addressed, aligning with the principles of secure software development practices and vulnerability management protocols.