Backdoors using webshells

Sometimes, we may also come across a file upload that is initially meant to upload files such as Excel documents and photos. But there are a few ways by which we can bypass it. In this recipe, we will see how to do that.

How to do it...

Let's perform the following steps:

1. Here, we have a web application that uploads a photo. So, let's upload an image here:

2. When we upload a photo, this is what we see on the application:

3. Let's upload a .txt file and see what happens. So, we create one with test as data:

4. After uploading it, you can see the following message on the window. Our image has been deleted:

5. This might mean our application is doing either a client-side or server-side...