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Persistent Cross-Site Scripting vulnerability in WordPress due to unsafe
processing of file names
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Han Sahin, July 2016

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Abstract
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A persistent Cross-Site Scripting (XSS) vulnerability has been found in
WordPress. An attacker can create a specially crafted image file name
which, when uploaded in WordPress, injects malicious JavaScript code
into the application. An attacker can use this vulnerability to perform
a wide variety of actions, such as stealing victims' session tokens or
login credentials, and performing arbitrary actions on their behalf.

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OVE ID
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OVE-20160724-0018

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Tested versions
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This issue was successfully tested on WordPress 4.5.3.

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Fix
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This vulnerability is resolved in WordPress 4.6.1 (Release Notes).

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Details
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https://sumofpwn.nl/advisory/2016/persistent_cross_site_scripting_vulnerability_in_wordpress_due_to_unsafe_processing_of_file_names.html

When an image with a file name such as cengizhansahinsumofpwn<img src=a onerror=alert(document.cookie)>.jpg is uploaded and viewed within WordPress the script code is executed

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Summer of Pwnage (https://sumofpwn.nl) is a Dutch community project. Its
goal is to contribute to the security of popular, widely used OSS
projects in a fun and educational way.