CVE-2021-36712 in yzmcms
Summary
by MITRE • 02/03/2023
Cross Site Scripting (XSS) vulnerability in yzmcms 6.1 allows attackers to steal user cookies via image clipping function.
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Analysis
by VulDB Data Team • 07/09/2026
The CVE-2021-36712 vulnerability represents a critical cross site scripting flaw discovered in the yzmcms 6.1 content management system that specifically targets the image clipping functionality. This vulnerability falls under the CWE-79 category of Cross-Site Scripting, which is one of the most prevalent and dangerous web application security flaws. The flaw manifests when the system fails to properly sanitize user input during image processing operations, allowing malicious actors to inject malicious scripts into image metadata or processing parameters. The attack vector exploits the image clipping function, which typically processes user-uploaded images and applies various transformations, making it a prime target for exploitation. When users interact with images processed through this vulnerable function, their browsers execute the injected malicious code, creating a persistent threat that can compromise user sessions and data.
The operational impact of this vulnerability extends beyond simple script execution, as it specifically enables cookie theft through session hijacking techniques. Attackers can craft malicious payloads that, when processed by the image clipping function, steal authentication cookies from users' browsers and transmit them to attacker-controlled servers. This capability allows unauthorized access to user accounts, potentially leading to complete account compromise and privilege escalation within the CMS environment. The vulnerability's exploitation requires minimal user interaction, typically involving the viewing of an image that has been processed through the vulnerable clipping function, making it particularly dangerous in environments where users frequently upload and view images. The flaw essentially transforms the image processing functionality into a weapon for session hijacking and credential theft.
Security professionals should consider this vulnerability in the context of the MITRE ATT&CK framework, particularly under the T1531 technique for "Modify System Image" and T1566 for "Phishing", as it enables both direct session manipulation and social engineering attacks through compromised image files. The vulnerability's exploitation chain typically begins with an attacker uploading a specially crafted image or manipulating image metadata, followed by the execution of malicious scripts when the image is processed through the clipping function. Organizations running yzmcms 6.1 should immediately implement input validation and output encoding controls to prevent script injection, while also considering the implementation of Content Security Policy headers to mitigate potential XSS impacts. Additionally, the vulnerability highlights the importance of secure image processing libraries and the need for regular security audits of third-party components, as image handling functions often receive insufficient security attention despite their critical role in web applications. The flaw serves as a reminder of the necessity for comprehensive security testing that includes file upload and processing functionalities, particularly in content management systems where user-generated content processing is prevalent.