CVE-2017-20239 in MDwiki
Summary
by MITRE • 04/12/2026
MDwiki contains a cross-site scripting vulnerability that allows remote attackers to execute arbitrary JavaScript by injecting malicious code through the location hash parameter. Attackers can craft URLs with JavaScript payloads in the hash fragment that are parsed and rendered without sanitization, causing the injected scripts to execute in the victim's browser context.
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Analysis
by VulDB Data Team • 04/12/2026
The vulnerability identified as CVE-2017-20239 resides within MDwiki, a lightweight web-based wiki application that relies heavily on client-side JavaScript for its functionality. This cross-site scripting vulnerability represents a critical security flaw that enables remote attackers to inject malicious code through the location hash parameter, effectively bypassing traditional input validation mechanisms that typically protect against such attacks. The vulnerability specifically exploits the application's failure to sanitize or properly validate hash fragments that are part of the URL, creating an attack surface where malicious JavaScript code can be seamlessly executed within the victim's browser environment.
The technical implementation of this vulnerability stems from MDwiki's improper handling of URL hash parameters during the rendering process. When a user navigates to a page with a malicious hash fragment, the application processes this parameter without adequate sanitization or escaping mechanisms, allowing attackers to inject arbitrary JavaScript code that executes in the context of the victim's browser. This flaw operates at the client-side level where the application's JavaScript engine parses and renders the hash content directly into the DOM without proper security controls, making it particularly dangerous as it can be exploited through simple URL manipulation without requiring any special privileges or authentication.
The operational impact of this vulnerability extends beyond simple script execution, as it provides attackers with the ability to perform a wide range of malicious activities within the victim's browser session. Attackers can leverage this vulnerability to steal session cookies, perform unauthorized actions on behalf of users, redirect victims to malicious websites, or even inject additional payloads that could lead to more severe consequences such as privilege escalation or data exfiltration. The remote nature of the attack means that victims can be compromised simply by visiting a maliciously crafted URL, making this vulnerability particularly dangerous in environments where users may encounter untrusted links or where social engineering tactics are employed.
This vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws in web applications, and demonstrates the classic pattern of insufficient input sanitization leading to code execution. From an ATT&CK framework perspective, this vulnerability maps to the T1059.007 technique related to script-based execution through browser-based attacks, while also potentially enabling techniques such as T1566 for social engineering and T1071.001 for application layer protocol usage. The attack vector leverages the trust relationship between the browser and the web application, exploiting the fact that legitimate web applications often need to process URL fragments for navigation purposes while failing to implement proper security controls for these inputs.
The mitigation strategy for this vulnerability requires immediate implementation of proper input sanitization and output encoding mechanisms within the MDwiki application. Developers should ensure that all hash fragment parameters are properly escaped and validated before being rendered or processed by the application's JavaScript components. The fix should include implementing a robust sanitization framework that removes or encodes potentially dangerous characters and JavaScript code patterns from URL hash parameters. Additionally, organizations should consider implementing Content Security Policy (CSP) headers to further limit the execution of inline scripts and provide an additional layer of protection against such attacks. Regular security audits and input validation testing should be conducted to ensure that similar vulnerabilities do not exist in other parts of the application's codebase.