1. "Extension sees data on pages for which it's activated, and might modify that all kept locally", and
2. "Extension sends all page information to The Cloud^W^W Somebody Else's Computer where it is probably being shared with umpteen third parties, advertising^W behavioural manipulation and surveillance organisations, and will be preserved in crystal until the Heat Death Of The Universe.
Why desktop, and most especially mobile platforms / operating systems fail to either distinguish or permit control between these two scenarios is ... utterly beyond me.
There is Steve Krenzel's recent account of being pressured, by both a Twitter marketing exec and the phone company requesting the feature, to track "when users leave their house, their commute to work, and everywhere they go throughout the day".
This should not even be possible, let alone invisible to the device owner.
<https://news.ycombinator.com/item?id=33511016>
<https://threadreaderapp.com/thread/1589700721121058817.html>
The reputational harm that this does to the company, to mobile computing, to Web 2.0, to the start-up sector, and to the infotech sector as a whole really cannot be overstated.
Burn it down.