CVE-2018-25248 Overview
CVE-2018-25248 is a persistent cross-site scripting (XSS) vulnerability affecting MyBB Downloads Plugin version 2.0.3. This vulnerability allows authenticated users with regular member privileges to inject malicious HTML and JavaScript code through the download title field. The injected payload is stored server-side and executes when administrators access the download validation interface in downloads.php.
Critical Impact
Attackers can execute arbitrary JavaScript in administrator browsers, potentially leading to session hijacking, privilege escalation, or administrative account compromise.
Affected Products
- MyBB Downloads Plugin 2.0.3
Discovery Timeline
- 2026-04-04 - CVE-2018-25248 published to NVD
- 2026-04-07 - Last updated in NVD database
Technical Details for CVE-2018-25248
Vulnerability Analysis
This vulnerability is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as Cross-Site Scripting. The MyBB Downloads Plugin fails to properly sanitize user-supplied input in the download title parameter before storing it in the database and subsequently rendering it in administrative pages.
The attack requires network access and low privileges (authenticated regular member), making it accessible to any registered forum user. The vulnerability specifically targets the administrative workflow where moderators and administrators review and validate user-submitted downloads.
Root Cause
The root cause lies in insufficient input validation and output encoding within the download submission handling code. When a user submits a new download entry, the plugin accepts the title parameter without proper sanitization for HTML entities or JavaScript code. The stored payload is then rendered without encoding when administrators view the download validation queue, allowing the malicious script to execute in the context of the admin's browser session.
Attack Vector
The attack is executed through the network by an authenticated attacker. The exploitation flow involves:
- An attacker registers or uses an existing regular member account on a MyBB forum with the Downloads Plugin installed
- The attacker submits a new download with malicious JavaScript embedded in the title field
- The payload is stored in the database pending administrator approval
- When an administrator navigates to downloads.php to validate pending downloads, the stored XSS payload executes in their browser
- The malicious script can steal session cookies, perform actions as the administrator, or redirect to phishing pages
The vulnerability requires user interaction from an administrator viewing the malicious content, but this is a normal administrative workflow that attackers can reasonably expect to occur.
Detection Methods for CVE-2018-25248
Indicators of Compromise
- Unusual JavaScript or HTML tags present in download title fields within the MyBB database
- Suspicious download submissions containing <script>, <img onerror=, <svg onload=, or other XSS payload patterns
- Administrator session tokens appearing in external server logs if exfiltration occurred
- Unexpected administrative actions or configuration changes following download validation activities
Detection Strategies
- Implement web application firewall (WAF) rules to detect XSS payloads in POST parameters targeting the downloads plugin
- Review database entries in the downloads table for stored HTML/JavaScript content
- Monitor administrator accounts for suspicious session activity or unexpected privilege escalations
- Deploy browser-based XSS protection headers and Content Security Policy (CSP) to mitigate payload execution
Monitoring Recommendations
- Enable detailed logging for the MyBB Downloads Plugin administrative actions
- Set up alerts for download submissions containing HTML special characters or JavaScript keywords
- Monitor for multiple failed or suspicious download submissions from single user accounts
- Implement regular security audits of user-generated content stored in the database
How to Mitigate CVE-2018-25248
Immediate Actions Required
- Disable the MyBB Downloads Plugin until a patched version is available or implement manual fixes
- Review and sanitize all existing download entries in the database for malicious content
- Implement input validation at the application level to reject submissions containing HTML or JavaScript
- Apply Content Security Policy headers to restrict inline script execution
Patch Information
No official vendor patch has been confirmed in the available data. Organizations should consult the MyBB Plugin Mod page for updates. The VulnCheck Advisory provides additional technical details. An Exploit-DB entry (#44400) documents the vulnerability for reference.
Workarounds
- Manually sanitize the download title input by adding htmlspecialchars() encoding before database storage
- Implement output encoding when rendering download titles in administrative pages
- Restrict download submission capabilities to trusted user groups only
- Deploy a web application firewall with XSS detection rules in front of the MyBB installation
- Enable and enforce Content Security Policy (CSP) headers to prevent inline script execution
Organizations should implement proper input sanitization by encoding user-supplied values before storage and ensuring proper output encoding when rendering content in administrative interfaces. The htmlspecialchars() or htmlentities() PHP functions should be applied to all user-controlled data displayed in HTML contexts.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
