EDIT: I believe I found the answer, it's something turned by this: https://ctatools.com/products/5065
Found some trash on the street that i'd like to take apart, but this screw is in my way.
It's like a hex bolt, but with 5 sides, and rounded (a bit like flower petals).
Here's another picture from the top:
I tried turning it with various tools (hard to get pliars in unfortunately), no success so far. The material is very soft, which doesn't help..
Oh ffs I didn’t notice it was inverted from the pics. Good catch. Someone really doesn’t want you to open that shit OP.
true, looking at second pic it's very hard to make out. I tried to capture it on the first picture, but it's not that good