24 bit

 When I opened the 24-bit challenge, there is a login page and a file to download. 

There is a file name b1.txt provided with this challenge. It's a text file but from the content in it, it doesn't look like a normal text file. 

The Content of the file is just random repetitive numbers, and it looks like a binary file. Now, from a little bit of google searching, I found that there are three types of binary file image, sound, or text. Clearly, it is not a text file. Then we try to change the extension of the file from "b1.txt" to "b1.jpg" because most likely it is an image file. After doing so it reveals the credentials of the login page easily.

Now we are going to put these credentials on the login page to solve the challenge.

And here you go we have solved the 24-bit challenge.

This method is commonly known as steganography, In which we hide data in the text file or some sort of other files where it is unrecognizable.

Note - If the challenge gives you an invalid CSRF token after putting the credentials, just try refreshing the page a few times and it will solve the problem.