Upload php reverse shell12/24/2023 ![]() ![]() When files are uploaded to the server, a range of checks should be carried out to ensure that the file will not overwrite anything which already exists on the server. Tools like Burp Suite or OWASP ZAP can be extremely helpful at this stage. Uploading files designed to provoke errors can help with this. If the website has server-side filtering, then we may need to take a guess at what the filter is looking for, upload a file, then try something slightly different based on the error message if the upload fails. If the website is employing client-side filtering, then we can easily look at the code for the filter and look to bypass it. With a basic understanding of how the website might be handling our input, we can then try to poke around and see what we can and cannot upload. Browser extensions such as Wappalyzer can provide valuable information at a glance about the site you are targeting. Intercepting upload requests with Burp Suite will also be handy. Scanning with a directory bruteforcer such as Gobuster is usually helpful in web attacks and may reveal where files are being uploaded to. Looking at the source code for the page is good to see if any kind of client-side filtering is being applied. Uploading and Executing Shells on a serverīypassing various kinds of Server-Side filtering The purpose of this room is to explore some of the vulnerabilities resulting from improper (or inadequate) handling of file uploads. Realistically speaking, an attacker with the ability to upload a file of their choice is very dangerous. With unrestricted upload access to a server (and the ability to retrieve data at will), an attacker could deface or otherwise alter existing content - up to and including injection malicious webpages which lead to further vulnerabilities such as XSS or CSRFīy uploading arbitrary files, an attacker could potentially also use the server to host and/or serve illegal content, or to leak sensitive information. This can lead to anything from relatively minor, nuisance problems all the way up to full RCE ( Remote Code Execution) if an attacker manages to upload and execute a shell. ![]() Unfortunately, when handled badly, file uploads can also open up severe vulnerabilities in the server. Be it a profile picture for a social media site, a report being uploaded to cloud storage or saving a project on GitHub the applications for file upload features are limitless. Changing the name of this function is sometimes sufficient enough to bypass AV if you are being blocked - you can read more about that here.The ability to upload files to a server has become an integral part of how we interact with web applications.
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