The challenge involved decoding the following string: V0VMQ09NRV9UT19USEVfQ0hBTExFTkdFUw==.

At first you may not know what type of encoding this is, but a tell-tale sign is the = at the end. This means that the string has been encoded using an algorithm called Base64. Not every Base64 string ends with ‘=’, but many will.

Now that we know what the string is, we can decode it. To do this, head over to CyberChef (or another similar site) and paste the string into the input box. Now if you look on the left side of the site, you will see a bar with a list of operations. Dragging the operation named ‘From Base64’ into the Recipe section in the middle will result in the input string being decoded.

This gives you the answer to the challenge - WELCOME_TO_THE_CHALLENGES.