Source: secalert@redhat.com
Multiple cross-site scripting (XSS) vulnerabilities in MyBB (aka MyBulletinBoard) 1.4.14, and 1.6.x before 1.6.1, allow remote attackers to inject arbitrary web script or HTML via vectors related to (1) editpost.php, (2) member.php, and (3) newreply.php.
MyBB versions 1.4.14 and 1.6.x before 1.6.1 are vulnerable to multiple cross-site scripting (XSS) attacks, allowing attackers to inject malicious scripts into web pages viewed by other users. This can lead to account compromise, session hijacking, and data theft by executing arbitrary code within the context of a user's browser.
Step 1: Payload Delivery: The attacker crafts a malicious payload containing JavaScript or HTML tags designed to exploit the XSS vulnerability. This payload is typically embedded within a post, profile information, or reply text.
Step 2: Payload Submission: The attacker submits the crafted payload to the MyBB forum through editpost.php, member.php, or newreply.php.
Step 3: Data Storage: The MyBB application stores the malicious payload in its database, associated with the attacker's post, profile, or reply.
Step 4: Victim Interaction: A legitimate user views the attacker's post, profile, or reply. The MyBB application retrieves the stored payload from the database.
Step 5: Payload Execution: The MyBB application renders the retrieved data in the user's browser. Because the payload was not properly sanitized, the browser executes the attacker's JavaScript or renders the HTML tags, leading to the XSS attack.
The vulnerability stems from insufficient input validation and output encoding within MyBB's code, specifically in editpost.php, member.php, and newreply.php. The application fails to properly sanitize user-supplied data before displaying it, allowing attackers to inject malicious JavaScript or HTML tags. The root cause is a lack of proper input validation and output encoding (e.g., HTML escaping) when handling user-provided data such as post content, profile information, or reply text. This allows attackers to craft payloads that, when rendered by the browser, execute arbitrary JavaScript code. The absence of proper contextual escaping for different output locations (e.g., within HTML attributes, JavaScript code blocks) exacerbates the issue.
While no specific APTs are definitively linked to this specific CVE, the widespread availability of exploits and the ease of exploitation make it a target for various threat actors. This vulnerability is a classic example of a low-hanging fruit and could be used by a wide range of attackers, from script kiddies to more sophisticated actors. This vulnerability is not listed on the CISA KEV at this time, but the age and nature of the vulnerability make it a prime candidate for inclusion if it were to be actively exploited in a widespread campaign.
Network Intrusion Detection Systems (IDS) can be configured to detect malicious payloads containing common XSS attack patterns (e.g., <script>, onerror, javascript:).
Web Application Firewalls (WAFs) can be deployed to filter malicious requests containing XSS payloads.
Review server logs for suspicious activity, such as unusual HTTP requests containing potentially malicious HTML or JavaScript code in parameters or POST data.
Monitor user activity for unusual behavior, such as a sudden increase in posts containing HTML or JavaScript code, or users accessing unusual URLs.
Examine the database for potentially malicious content, such as posts or profile information containing suspicious HTML or JavaScript tags.
Upgrade to MyBB version 1.6.1 or later, or apply the security patches provided by the MyBB developers.
Implement proper input validation to sanitize all user-supplied data before storing it in the database.
Implement output encoding (e.g., HTML escaping) to ensure that user-supplied data is properly rendered in the browser.
Use a Content Security Policy (CSP) to restrict the sources from which the browser can load resources, mitigating the impact of successful XSS attacks.
Regularly scan the web application for vulnerabilities using automated tools.
Implement a Web Application Firewall (WAF) to filter malicious requests.