Plugin retrieving results even after uninstallation

I'm using the WP REST API plugin to get info from my website. I built a little plugin that uses this one. In my plugin I'm just removing some fields from the responses that I don't need.

Everything was working well until some hours ago the filter by category I was applying when requesting the categories stopped working. It started retrieving all posts.

I tried on an HTTP Request tool (POSTMAN) invoking the WP REST API and it doesn't filter too. My request URL is like this:

http://my.domain/wp-json/wp/v2/posts?_embed=truefilter[cat]=77

But if I try:

http://my.domain/wp-json/wp/v2/posts?_embed=truecategories=77

It works.

So I deactivated (and even uninstalled) the WP REST API plugin, made the request and it was still retrieving me the posts!

I have 2 questions:

• Why is an uninstalled plugin still retrieving results?
• Is it possible another plugin to be the responsible for retrieving the results? I checked the active plugins for another that could do something like this but didn't find anything...

I'm new using Wordpress so probably I'm not aware of something...

UPDATE

Wordpress version: 4.7