Need some security advice for using a custom browser extension from a 3rd party developer

I'm in the market to hire a developer to help me out with a chrome browser extension that can read the content of web pages. Given that most extensions can read what your browse on the internet, what are the risks of going this route? Would a connection montitor/blocker like Little Snitch be successful in stopping any captured data from being transmitted to the 3rd party? I realize that I should ideally be able to trust a developer I'm working with, but I'm just trying to play it safe….

Need some security advice for using a custom browser extension from a 3rd party developer