Edit:
WARNING: DO NOT USE.
I downloaded the xpi (add-on file) and was looking in the source code, its definitely doing something dodgy. It's downloading a file from the devs homepage called https://ad.resourcefulman.net/banner/ad-locations.txt and seems to be injecting adverts etc into the web pages, and redirecting other pages. I am reporting this add-on.

Original post:
I am pretty sure this addon is malicious.
When visiting AliExpress, I get getting redirected to weird versions of the site. After some investigation I found reddit post stating "Best.aliexpress is known to be a redirection/affiliate link. Clean all cookies of your browser. then revisit aliexpress." After I used "forget site", it started happening almost immediately again. I disabled all my add-ons and re-enabled them one at a time, I found that after re-enabling "600% Sound Volume", the redirects would consistently happen. If I forgot site, and had 600% addon disabled, I could browse Ali indefinitely, however as soon as I re-enabled 600%, all subsequent Ali browsing would be getting redirect to the affiliate link.