CVE-2008-0751 in Serendipity Freetag-plugin
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the Freetag before 2.96 plugin for S9Y Serendipity, when using Internet Explorer 6 or 7, allows remote attackers to inject arbitrary web script or HTML via the PATH_INFO to plugin/tag/.
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Analysis
by VulDB Data Team • 10/10/2025
The vulnerability described in CVE-2008-0751 represents a classic cross-site scripting flaw within the Freetag plugin for the S9Y Serendipity blogging platform. This security weakness specifically affects versions prior to 2.96 and manifests when the application processes user input through the PATH_INFO parameter in the plugin/tag/ endpoint. The vulnerability is particularly concerning as it leverages the Internet Explorer 6 and 7 browsers, which were widely deployed during the late 2000s period when this flaw was discovered. The attack vector involves remote adversaries who can inject malicious web script or HTML code directly into the application's response handling mechanism.
The technical root cause of this vulnerability stems from insufficient input validation and output encoding within the Freetag plugin's processing of the PATH_INFO parameter. When Internet Explorer 6 or 7 encounters the maliciously crafted input, the browser renders the injected scripts within the context of the vulnerable web application, effectively allowing attackers to execute arbitrary code in the victim's browser session. This behavior aligns with CWE-79, which categorizes cross-site scripting vulnerabilities as weaknesses that occur when an application fails to properly validate or encode user-supplied data before incorporating it into dynamic web content. The vulnerability specifically demonstrates how improper sanitization of input parameters can lead to unauthorized script execution within the browser context of legitimate users.
The operational impact of this vulnerability extends beyond simple data theft or defacement, as it provides attackers with the capability to hijack user sessions and perform actions on behalf of authenticated users. In the context of a blogging platform like Serendipity, this could enable attackers to modify blog content, steal administrator credentials, or redirect users to malicious websites. The fact that this vulnerability specifically targets older Internet Explorer versions makes it particularly dangerous in environments where legacy browser support is maintained, as these browsers often lack modern security mitigations that would otherwise prevent such attacks from succeeding. The vulnerability also demonstrates how plugin-based applications can introduce security risks that extend beyond the core application functionality, highlighting the importance of thorough security testing for third-party extensions.
Mitigation strategies for this vulnerability should focus on immediate patching to upgrade to Freetag version 2.96 or later, which would contain the necessary input validation and output encoding fixes. Organizations should also implement additional defensive measures such as input sanitization at the web application firewall level and regular security assessments of plugin components. The vulnerability serves as a reminder of the critical importance of keeping all application components updated, as the patched version would contain proper validation routines that prevent the PATH_INFO parameter from being directly embedded into HTML output without appropriate encoding. From an ATT&CK perspective, this vulnerability would be categorized under T1566.001 for initial access through malicious web content, and potentially T1059.001 for command and control through script injection techniques. Organizations should also consider implementing Content Security Policy headers as an additional defense-in-depth measure to prevent unauthorized script execution even if such vulnerabilities are present in other components of the application stack.