How to run a script in a browser without extensions?

Question

userscript

By the way, does it have malicious functionality? (link to text file with source code) https://docs.google.com/document/d/1hLk_Uj0SHnmhPw...

Answer 1

You can run it in the browser console. The script will be executed in the context of the open page.
The link does not show the source - it is only for individual accounts. Copy to pastebin or gist.github.com