Arbitrary file upload vulnerability in Wordpress wpDiscuz plugin

Today i was going through Twitter and in one of the Tweet, I got to know about the vulnerability in "Wordpress wpDiscuz plugin". This vulnerability is discovered by Wordfence Team. 
 
Vulnerability is simple and can be exploited if user has permission to upload image as attachment.
Plugin is just checking for file "Magic Number" and not performing any check for file extension.

Here an attacker can take advantage to perform "Remote Code Execution" by following below mentioned steps:

Step 1: Rename image file to .php extension file
 
Step 2: open renamed file in text editor, append PHP code in the end of the file and save it.

Step 3: Go to website comment section and click to comment in comment box.

Step 4: Web application comment box will have option for image file attachment. Click the icon to browse the file which we modified in step 2.

Step 5: Fill the form with relevant information and post the comment.

Step 6: Web application will show the uploaded attached image file. Copy the image file URL.

 Step 7: In copied URL, remove the "-" symbol and image file dimension (it will be in the end) before .php extension.

 Step 8: Browse the URL and we have access to web shell.

Thanks for reading.

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