CVE-2013-7343 in Flowplayer HTML5
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in flowplayer.swf in the Flash fallback feature in Flowplayer HTML5 5.4.3 allows remote attackers to inject arbitrary web script or HTML by using URL encoding within the callback parameter name. NOTE: this vulnerability exists because of an incomplete fix for CVE-2013-7342.
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Analysis
by VulDB Data Team • 05/08/2026
The vulnerability described in CVE-2013-7343 represents a cross-site scripting flaw within the Flowplayer HTML5 media player version 5.4.3, specifically affecting the Flash fallback mechanism. This issue demonstrates how security patches can sometimes introduce new vulnerabilities when they fail to address all potential attack vectors. The flaw exists in the flowplayer.swf component that serves as a fallback for browsers that do not support HTML5 video playback, creating a persistent security risk that extends beyond the primary HTML5 implementation.
The technical exploitation of this vulnerability occurs through manipulation of the callback parameter name within URL encoding, allowing remote attackers to inject malicious web scripts or HTML code into the application's response. This XSS vulnerability specifically targets the Flash fallback feature, which means that when HTML5 playback fails or is disabled, the system reverts to Flash-based playback where the malicious input can be executed. The vulnerability is particularly concerning because it leverages the URL encoding technique to bypass security measures that might otherwise detect or sanitize the input, making it more difficult to identify and prevent.
The operational impact of this vulnerability extends beyond simple script injection, as it can potentially allow attackers to execute malicious code within the context of the user's browser session. This could lead to session hijacking, data theft, or the execution of unauthorized actions on behalf of the user. The fact that this vulnerability exists due to an incomplete fix for CVE-2013-7342 demonstrates poor security patch management and highlights the complexity of securing multimedia applications that rely on multiple technology stacks including both HTML5 and Flash components. Such vulnerabilities can be exploited to deliver malware, steal sensitive information, or compromise user sessions across multiple websites that implement Flowplayer.
Security professionals should recognize this vulnerability as a variant of CWE-79 which represents Cross-Site Scripting in the context of web applications, and it aligns with ATT&CK technique T1566.001 for initial access through spearphishing attachments and T1059.007 for command and scripting interpreter through Flash. The remediation approach requires immediate patching of the Flowplayer HTML5 component to address the incomplete fix, implementation of proper input validation and sanitization for all callback parameters, and consideration of deprecating Flash-based fallback mechanisms in favor of more secure HTML5 implementations. Organizations should also implement content security policies to limit the execution of malicious scripts and conduct regular security assessments of multimedia components to prevent similar vulnerabilities from emerging in the future.