Looking at the code above, we can clearly say that the file upload is possible only if the MIME type of the file being uploaded is equal to “image/jpeg.” So, let us see how a developer can implement this. If not, the file will not be uploaded, and the user will be shown a custom error. If these two match, the file will be uploaded. This value will be checked against the value that the developer wants to allow. This variable holds the MIME type of the file being uploaded. This can be done using the variable “$_FILES” Usually, developers check if the MIME type of file being uploaded is something that is intended. When a file is uploaded, it returns a MIME type. The attacker now should be able to access the entire file system of the server as shown below.īypassing Content-type verification (parameter tampering)įor most web developers, the first technique to prevent file upload vulnerabilities is to check the MIME type. In our case, the file is uploaded in a folder called “uploads.” Otherwise, it is not possible to access the shell being uploaded. Note: Attacker should be able to find the location of the uploaded file on the server.
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