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+---- Thread: [PHP] File Upload Issue (Found Image Backdoor) (/showthread.php?tid=5701288)
File Upload Issue (Found Image Backdoor) - Numinous - Aug 22, 2017
Please look at this code - https://gyazo.com/f292c173dbebccde90b1a8b4cd02b7ea
whcih i found in one of the web server and that site is using some FILE UPLOAD functionality and someone uploaded a valid .GIF file and when i extracted that gif file with the help of Notepad and then i found a file upload backdooring code in the middle of the file.
So my question is, how a hacker can execute this backdooring code even that file upload code is very much secured.
* - Payload - Aug 22, 2017
The code will be executed when the image is loaded. Have a look at some other examples to understand how this works.
https://hackerone.com/reports/135072
https://secgeek.net/bookfresh-vulnerability/
* - Numinous - Aug 23, 2017
I already read that links, and i tried to open that .GIF file in my browser and it actually displays a image but i'm unable to execute that PHP code.
I tried all best possible ways like .gif.php, .php.gif, .gif.php2, .gif.php3, .php etc
* - Payload - Aug 23, 2017
(Aug 23, 2017 12:06 AM)Numinous Wrote: I already read that links, and i tried to open that .GIF file in my browser and it actually displays a image but i'm unable to execute that PHP code.
I tried all best possible ways like .gif.php, .php.gif, .gif.php2, .gif.php3, .php etc
Use ASCII encoding, you are probably saving the file UTF-8
Send a paste, i'm too lazy to type it out.
* - Charger - Aug 24, 2017
If you send proper headers they shouldn't be able to execute it.
How did it get uploaded?
* - Ceanko - Aug 24, 2017
Not enough information really, but this should help you: ForceType.
Like Charger said, headers. Although I suggest you still fix the issue at the root; checking if an image is valid.