This venerability is known as WordPress Easy Comment Upload Venerability.
Index of /wp-content/plugins/easy-comment-uploads
Open Google and enetr any dork which Given,
Now selct any website
and goto this url site.com/wp-content/plugins/easy-comment-uploads/upload-form.php
You'll Got Upload Option here :)
Now Upload Your Deface ....
and check it here site.com/wp-content/uploads/2011/05/yourfilehere
Note :- In some websites you can Upload your deface in txt on only ... and you can upload shell in 50% sites only ... upload shell in image format ex; shell.asp;.jpg
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