Halloween is here

[Jijel]

Halloween is coming up really fast and my university set up a quest. I've solved the first 2 challenges, but now I'm stuck.
All I have is the following string: Mzg0Mzg5MTUgODE4NTg3MjQ=
And the following hints from the organizer: "They use it in injection attacks", "it's halloween related", "That is an odd string. Maybe it's not what it looks like" and "Maybe it's a code".
I've looked for all sort of injection attacks, found nothing related to halloween in any way. Found out about the Halloween Problem (google it), but that's not the answer, and no information about it led me to the answer. I've also tried Caesar Cipher to no avail. I'm stuck. I have no idea, I've took an one hour break from it and came back thinking abut this forum.
I'm only asking for ideas, something to put me on a new track.

Instant edit: I've asked the following question "Is it crypto related? I've tried Caesar cipher, but nothing came out of it." and they answered me with "It means that you have not tried enough".
I'll keep trying with Caesar and some substitution.

[eulerscheZahl]

I wouldn't call the method used crypto. More like a compression. Wikipedia lists it as Binary-to-text encoding. This method is used when you attach an image to an email for example.
I can extract two numbers out of the string.

[Jijel]

thanks for the answer.
It was something in base64. Didn't get the time to decode it.
I tried base64 before the quest ended, but without much success, there was something more I had to see which I didn't.