You need to ensure an appropriate file name, use a whitelist of file extensions, limit file size, and perform standard security measures.
IMAGETYPE PHP HOW TO
This is only prevented by using a whitelist of file extensions. and easy to understand Web building tutorials with lots of examples of how to use HTML, CSS, JavaScript, SQL, Python, PHP, Bootstrap, Java, XML and more. To review, open the file in an editor that reveals hidden Unicode characters. Yay! I've deleted all your uploads assuming you're running on a Linux webserver.Įven doing a deeper check on the validity of the image won't help, because I could include my malicious script in the metadata of the image. php-imagetype-constants This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. The server finds the starting 
The magic number bypasses exif_imagetype. I construct 'shell.php' with the JPEG magic number 0xFFD8FFE0 followed by the string < passthru (GET 'cmd') >.
I construct "shell.php" with the JPEG magic number 0xFFD8FFE0 followed by the string. Without more knowledge of your software, it's hard to make a judgement, but consider this example: That function simply checks the magic number at the beginning of the file, so more checks are needed.
It's a bit more complicated that just running exif_imagetype.
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