CVE-2023-5718 in Devtools Extension
Summary
by MITRE • 10/25/2023
The Vue.js Devtools extension was found to leak screenshot data back to a malicious web page via the standard `postMessage()` API. By creating a malicious web page with an iFrame targeting a sensitive resource (i.e. a locally accessible file or sensitive website), and registering a listener on the web page, the extension sent messages back to the listener, containing the base64 encoded screenshot data of the sensitive resource.
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Analysis
by VulDB Data Team • 10/25/2023
The vulnerability identified as CVE-2023-5718 represents a critical security flaw in the Vue.js Devtools browser extension that demonstrates a sophisticated data exfiltration mechanism through improper use of the postMessage API. This vulnerability specifically affects developers who utilize the Vue.js Devtools extension for debugging and development purposes, creating a dangerous attack surface where sensitive information can be inadvertently exposed to malicious actors. The flaw arises from the extension's failure to properly validate message origins and destinations, allowing malicious web pages to establish communication channels that can capture and transmit screenshot data from targeted resources.
The technical implementation of this vulnerability leverages the standard web platform API postMessage which is designed for secure cross-origin communication between different browsing contexts. However, the Vue.js Devtools extension improperly handles incoming messages and fails to implement proper origin validation checks before processing screenshot data. When a malicious web page creates an iframe targeting a sensitive local resource or website, and registers a message listener, the extension's code path inadvertently sends base64 encoded screenshot data back to the attacker's page through the postMessage mechanism. This behavior violates fundamental security principles of the postMessage API which requires explicit origin validation to prevent unauthorized data leakage.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can lead to the exposure of sensitive development environments, internal network resources, and confidential data that developers might be accessing through their local development setups. Attackers can exploit this vulnerability to capture screenshots of local files, development servers, or sensitive websites that are accessible within the browser context where the extension is installed. The base64 encoding of screenshot data does not provide any meaningful security protection against this type of attack, as the encoded content can be easily decoded and analyzed by the malicious actor. This vulnerability particularly affects developers working in environments where local development servers are accessible via localhost or internal network addresses, as these resources are prime targets for such attacks.
Security researchers have classified this vulnerability under CWE-200 (Information Exposure) and potentially CWE-94 (Code Injection) depending on the specific implementation details, as it demonstrates a clear failure in proper input validation and secure communication practices. The attack pattern aligns with techniques described in the MITRE ATT&CK framework under T1566 (Phishing) and T1071.004 (Application Layer Protocol: DNS) where attackers establish malicious web pages to capture sensitive data from legitimate browser extensions. Organizations and developers should immediately update to patched versions of the Vue.js Devtools extension and implement additional security measures such as restricting browser extension permissions and monitoring for unusual postMessage activity. The vulnerability highlights the importance of proper API security practices and demonstrates how seemingly innocuous extension functionality can become a significant security risk when proper validation and sanitization controls are not implemented.