CVE-2012-6550 in ZeroClipboard
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in ZeroClipboard before 1.1.4 allows remote attackers to inject arbitrary web script or HTML via "the clipText returned from the flash object," a different vulnerability than CVE-2013-1808.
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Analysis
by VulDB Data Team • 06/25/2025
The vulnerability identified as CVE-2012-6550 represents a cross-site scripting flaw in the ZeroClipboard library prior to version 1.1.4. This security weakness specifically affects the handling of clipText data returned from flash objects, creating a pathway for remote attackers to execute malicious web scripts or HTML code within victim browsers. The vulnerability operates through the flash object's return mechanism, where user-supplied data flows directly into the web application without proper sanitization or validation. This particular XSS vector differs from CVE-2013-1808, indicating that the attack surface and exploitation techniques are distinct within the same software ecosystem. The ZeroClipboard library serves as a client-side tool designed to facilitate clipboard operations by leveraging flash technology, making it a common component in web applications requiring copy-paste functionality. The flaw arises from inadequate input validation and output encoding practices when processing data from the flash object's clipText parameter.
The technical implementation of this vulnerability stems from the improper handling of data returned by flash objects within the ZeroClipboard library. When the flash component executes and returns clipText data to the JavaScript environment, the application fails to sanitize or encode this information before incorporating it into web pages or DOM elements. This creates a classic XSS condition where attacker-controlled data can be injected into the browser context, potentially leading to session hijacking, credential theft, or redirection to malicious sites. The vulnerability's exploitation requires an attacker to control or influence the content of clipText values that flow through the flash object, which could occur through various means including manipulated user inputs, compromised data sources, or injection points within the application's data processing pipeline. The attack typically involves crafting malicious content within the clipText parameter that, when processed by the vulnerable library, executes unintended code in the victim's browser context.
The operational impact of CVE-2012-6550 extends beyond simple script execution, as it can enable attackers to perform sophisticated attacks against users of vulnerable applications. This includes the potential for credential harvesting through session token theft, redirection to phishing sites, defacement of web pages, or the execution of additional malicious payloads through the compromised clipboard functionality. The vulnerability is particularly concerning because it operates at the client-side level, making it difficult to detect through traditional server-side security measures. Applications using ZeroClipboard before version 1.1.4 become susceptible to attacks that can persist across user sessions and potentially affect multiple applications if the same vulnerable library instance is shared across different web contexts. The attack vector is particularly dangerous in environments where users interact with untrusted content, as the vulnerability can be exploited through social engineering techniques or by compromising data sources that feed into the clipboard functionality.
Organizations should prioritize immediate remediation by upgrading to ZeroClipboard version 1.1.4 or later, which addresses this specific XSS vulnerability through proper input sanitization and output encoding mechanisms. The mitigation strategy should include comprehensive code review processes to identify all instances where clipText data flows through the application, implementing strict validation and encoding for any data originating from flash objects. Security teams should also consider implementing content security policies that restrict script execution and limit the potential impact of successful XSS attacks. The vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws in web applications, and represents a classic example of insecure data handling practices that violate secure coding principles. From an ATT&CK framework perspective, this vulnerability maps to techniques involving client-side exploitation and session management compromise, making it relevant to both the initial access and privilege escalation phases of an attack lifecycle. Additionally, organizations should establish monitoring procedures to detect unusual clipboard operations or unexpected data flows that might indicate exploitation attempts against this vulnerability.