This extension can grab the words from webpage, it is developed to do browser completion for Vim and VS Cdoe.
There is a local server run on the background. That server receives the words grabbed by this extension from you web page and use the words for Vim/VSCode completion candidates.
So the extension must has permissions for the local system to send words text to the local server. Normally they use 8888 port to communicate with each other.
In order to complete the words from you browser, firstly you should install coc-browser for Vim, visit:
https://github.com/voldikss/coc-browser for more details.
That server receives the words grabbed by this extension from you web page and use the words for NeoVim/Vim completion candidates.
The extension must has permissions for the local system to send words text to the local server. Normally they use 8888 port to communicate with each other.