CVE-2020-18336 in Typora
Summary
by MITRE • 10/25/2023
Cross Site Scripting (XSS) vulnerability found in Typora v.0.9.65 allows a remote attacker to obtain sensitive information via the PDF file exporting function.
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Analysis
by VulDB Data Team • 10/28/2023
The CVE-2020-18336 vulnerability represents a cross site scripting flaw in the popular markdown editor Typora version 0.9.65 that specifically impacts the PDF export functionality. This vulnerability falls under the CWE-79 category of Cross-Site Scripting, which is one of the most prevalent web application security weaknesses identified by the CWE organization. The flaw manifests when users attempt to export markdown documents to PDF format, creating a potential attack vector that could be exploited by remote adversaries to execute malicious scripts within the context of the victim's browser session.
The technical implementation of this vulnerability stems from insufficient input validation and output encoding within the PDF export module of Typora. When processing markdown content that contains specially crafted malicious payloads, the application fails to properly sanitize user-supplied data before incorporating it into the PDF generation process. This inadequate sanitization allows attackers to inject malicious JavaScript code that gets executed when the exported PDF is opened in a web browser. The vulnerability specifically targets the PDF export function, making it particularly concerning for users who frequently export documents containing potentially untrusted content or collaborate with external parties who might provide malicious input.
The operational impact of CVE-2020-18336 extends beyond simple script execution, as it can potentially enable attackers to access sensitive information stored within the user's browser context. An attacker could leverage this vulnerability to steal session cookies, perform unauthorized actions on behalf of the victim, or exfiltrate data from the victim's system. The attack surface is particularly broad since PDF files are commonly shared and opened across different platforms and browsers, increasing the likelihood of successful exploitation. This vulnerability aligns with ATT&CK technique T1059.007 for JavaScript execution and T1566 for spearphishing with a malicious attachment, as users might be tricked into opening malicious PDFs generated through this vulnerability.
Organizations and individual users utilizing Typora for document creation and sharing should immediately update to the patched version of the software to mitigate this risk. The vulnerability demonstrates the critical importance of proper input validation and output encoding in applications that process user-supplied content, particularly in export functionalities that generate files for external consumption. Security practitioners should consider implementing additional monitoring for suspicious PDF file activities and ensure that all software components are regularly updated to address known vulnerabilities. The incident underscores the necessity of following secure coding practices and conducting thorough security testing of export and file generation features to prevent similar cross site scripting vulnerabilities from being introduced in future software releases.