This is based on the infosec Institute Noob CTF http://ctf.infosecinstitute.com/. In Level 2.
Step one :
The Image is broken but exists in the image folder. so we download it. first thing is identify if it is indeed an image. We can use filealyzer for this.
Now in the Hex tab we see no indication of an image header. Notice though a base64 string is in the file .
Alternatively at this point you can rename the file to a .txt and copy the string.
To decode the string you can use the hackbar extension.
From this we get the answer.