CVE-2020-28459 in markdown-it-decorate
Summary
by MITRE • 07/25/2022
This affects all versions of package markdown-it-decorate. An attacker can add an event handler or use javascript:xxx for the link.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 07/26/2022
The vulnerability identified as CVE-2020-28459 affects the markdown-it-decorate package, which is commonly used for processing markdown content in web applications. This security flaw represents a significant concern for developers and security professionals as it exposes applications to potential cross-site scripting attacks through improper input validation. The package's failure to adequately sanitize user-provided content creates an environment where malicious actors can inject harmful JavaScript code into markdown documents. The vulnerability specifically manifests when the package processes links that contain event handlers or javascript protocols, allowing arbitrary code execution in the context of the victim's browser. This issue impacts all versions of the affected package, indicating that it has been present for an extended period without proper mitigation.
The technical flaw stems from insufficient sanitization of link attributes within the markdown processing pipeline. When users submit markdown content containing links with javascript protocols or event handlers such as onclick= or href=javascript:, the package fails to properly validate or escape these inputs before rendering them in the final HTML output. This oversight creates a direct path for attackers to inject malicious scripts that can execute in the context of legitimate users browsing the affected web applications. The vulnerability aligns with CWE-79, which describes improper neutralization of input during web page generation, and specifically relates to the improper handling of untrusted data in web applications. The flaw operates at the application layer and can be exploited through user input fields, comment sections, or any mechanism that accepts markdown content for processing and display.
The operational impact of this vulnerability extends beyond simple code injection, as it can enable attackers to perform a wide range of malicious activities including session hijacking, data theft, and redirection to malicious sites. When exploited, the vulnerability allows attackers to execute JavaScript code within the context of the victim's browser session, potentially leading to complete compromise of user accounts and sensitive data exposure. Applications that rely on markdown-it-decorate for user-generated content processing are particularly vulnerable, including content management systems, wikis, forums, and documentation platforms. The attack vector requires minimal technical expertise and can be automated, making it attractive to threat actors. The vulnerability's persistence across all versions of the package means that organizations using this library have likely been exposed to this risk for an extended period, creating a substantial attack surface that could be exploited by both automated scanners and targeted attacks.
Mitigation strategies for CVE-2020-28459 should focus on immediate remediation through package updates or replacement with secure alternatives. Organizations should implement strict input validation and sanitization measures that filter out javascript protocols and event handlers from user-provided links before processing. The implementation of content security policies can provide additional protection layers by restricting script execution and preventing unauthorized code injection. Security teams should conduct comprehensive audits of all applications using the affected package to identify and remediate instances where user-generated markdown content is processed. Regular security testing and dependency scanning should be implemented to detect similar vulnerabilities in other third-party libraries. The ATT&CK framework categorizes this vulnerability under T1203, which involves exploitation of web applications through input validation flaws, and T1059, which covers execution through scripting languages. Organizations should also consider implementing web application firewalls and monitoring systems to detect and prevent exploitation attempts targeting this specific vulnerability.