CVE-2017-9337 in Markdown on Save Improved Plugin
Summary
by MITRE
The Markdown on Save Improved plugin 2.5 for WordPress has a stored XSS vulnerability in the content of a post.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 10/13/2019
The Markdown on Save Improved plugin version 2.5 for WordPress contains a critical stored cross-site scripting vulnerability that allows attackers to inject malicious scripts into post content. This vulnerability arises from insufficient input validation and output sanitization within the plugin's handling of user-supplied markdown content. When administrators or users create or edit posts containing malicious payloads, the vulnerability enables persistent XSS attacks that can execute arbitrary JavaScript code in the browsers of unsuspecting visitors. The flaw specifically affects the plugin's processing of markdown content that gets stored in the WordPress database and subsequently rendered back to users without proper sanitization.
The technical exploitation of this vulnerability occurs when malicious markdown content containing script tags or other XSS payloads is saved to a post. Upon subsequent viewing of the post, the stored malicious code executes in the context of the victim's browser, potentially allowing attackers to steal session cookies, perform actions on behalf of users, or redirect them to malicious sites. The vulnerability represents a classic stored XSS flaw that can be categorized under CWE-79 as improper neutralization of input during web page generation. This weakness enables attackers to establish persistent footholds within WordPress environments by leveraging the trusted relationship between the legitimate plugin and the WordPress installation.
The operational impact of CVE-2017-9337 extends beyond simple script execution, as it can lead to complete compromise of WordPress administrative sessions and unauthorized content modification. Attackers can leverage this vulnerability to inject backdoors, modify post content, or even escalate privileges within the WordPress environment. The vulnerability affects not only individual users but also entire WordPress installations that rely on the Markdown on Save Improved plugin for content management. This issue aligns with ATT&CK technique T1546.001 for persistence mechanisms and T1566 for credential access through social engineering via compromised content.
Security professionals should immediately disable or uninstall the affected plugin version 2.5 and implement comprehensive input validation measures for all user-generated content. Organizations should also consider implementing Content Security Policy headers to mitigate the impact of potential XSS attacks, and maintain updated security monitoring to detect unauthorized content modifications. Regular security audits of WordPress plugins and themes remain essential for identifying similar vulnerabilities, with particular attention to plugins handling user input and content rendering. The vulnerability demonstrates the critical importance of proper input sanitization and output encoding in web applications, particularly in content management systems where user-generated content processing is common.