@Antya2 actually it is both. It shows the reviews left by guests. (not always, it's not so perfect) but here's an example of a recent guest. on the guest profile you can see the review I left, plus the guests' review. I won't share the rest (even though reviews are public) but the whole page shows the reviews left by the host and the guest review underneath. It's very handy!
I haven't had any malware issues (I am on a Mac though) but it's a chrome extension, you don't download anything to use it. None of the reviews mention malware, and the few 1* reviews are as amusing as a silly guest review, and also quite old. It is currently available in the Chrome store.