Can someone help me identify this Brazilian spider?
Interesting!  See those long spines on the legs?  Only two groups of spiders (that come to mind, anyway) have that sort of arrangement:
Lynx Spiders (Family Oxyopidae) and Pirate Spiders (Family Mimetidae).
Lynx Spiders are wandering hunters, and the ones I'm familiar with tend to have a body shape more like the familiar Grass Spiders (longish, tear-drop shaped abdomen and hunters cephalothorax - roughly rectangular, and often very blocky at the face.
For instance:
https://bugguide.net/node/view/1965


https://bugguide.net/node/view/1489229/bgimage

So, your spider looks to be a South American Lynx Spider, which unfortunately I'm not at all knowledgeable about.

I'm going to discount Pirate Spiders as a possibility, even with the association there with a bit of web (Pirate Spiders invade other species' webs and kill the occupants), because they're much more 'orb-weaver'-like in their general body shape.  This one is so Lynx Spider-like that I am pretty confident that it is one of those.