You can update your FCKEditor module (check: http://drupal.org/node/1482442)
Or,
you can use CKEditor instead of FCKEDITOR. See: http://drupal.org/project/ckeditor
I have faced similar security issue using CKEditor. And I have following the below steps:
Here is the process to update ckeditor and ckfinder:
- Update CKeditor version 6.x—1.13
- Download CK Finder latest version 2.3
- Unzip the ckfinder in sites/all/module/contrib/ckeditor/ckfinder
- Open /all/module/contrib/ckeditor/ckfinder/config.php
Comment out the CheckAuthentication() function
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Add the below two lines
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$baseUrl may differ depends on products.
- Open /contrib/ckeditor/ckfinder/config.js
add the below lines:
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Note: I would like to request all to prepare a set of allowed and denied extensions
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One more additional issue: Add cookie_domain in sites/default/settings.php file.