CVE-2020-9447 in GwtUpload
Summary
by MITRE
The file-upload feature in GwtUpload 1.0.3 allows XSS via a crafted filename.
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Analysis
by VulDB Data Team • 05/11/2025
The vulnerability identified as CVE-2020-9447 resides within the GwtUpload 1.0.3 library, which is commonly used in web applications for handling file uploads. This particular implementation suffers from a cross-site scripting flaw that occurs when the application processes user-supplied filenames during the upload process. The issue stems from insufficient input validation and sanitization of file metadata, specifically the filename parameter that gets rendered in the application's user interface without proper encoding or filtering mechanisms.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious filename containing script tags or other XSS payloads that get executed in the context of other users' browsers. When the application displays the filename in its user interface, such as in upload status messages or file listings, the malicious content gets interpreted as executable JavaScript code rather than plain text. This vulnerability falls under CWE-79 which specifically addresses cross-site scripting flaws, and it represents a classic case of improper output encoding where user-controllable data enters the application's rendering pipeline without adequate sanitization.
The operational impact of this vulnerability extends beyond simple script execution, as it can potentially enable attackers to steal session cookies, perform actions on behalf of authenticated users, or redirect victims to malicious websites. In a web application context, this could lead to privilege escalation attacks, data theft, or complete compromise of user accounts depending on the application's access controls and the privileges of the affected users. The vulnerability affects any application using GwtUpload 1.0.3 that displays uploaded filenames in the user interface without proper HTML encoding, making it particularly dangerous in environments where multiple users interact with uploaded content.
Mitigation strategies for CVE-2020-9447 should focus on implementing proper input validation and output encoding practices. Organizations should immediately upgrade to a patched version of GwtUpload if available, or implement custom sanitization routines that strip or encode potentially dangerous characters from filenames before rendering them in the user interface. The solution aligns with ATT&CK technique T1203 which involves exploiting weaknesses in input validation to execute malicious code. Additional defensive measures include implementing content security policies, using secure coding practices that enforce proper HTML escaping, and conducting regular security testing of file upload functionalities to identify similar vulnerabilities in other components of the application stack.