The headline seems pretty misleading. Here’s what seems to actually be going on: > Every time you open LinkedIn in a Chrome-based browser, LinkedIn’s JavaScript executes a silent scan of your installed browser extensions. The scan probes for thousands of specific extensions by ID, collects the results, encrypts them, and transmits them to LinkedIn’s servers. This does seem invasive. It also seems like what I’d expect…
Why is JavaScript running in a page even allowed to know what extensions I have? Is this also what sites use to see I've got an ad blocker? Just run everything in a safe environment that it can't look out of.
Since the extensions are running on the same page as LinkedIn (some of them are explicitly modifying the LinkedIn the website) it's impossible to sandbox them so that linked in can't see evidence of them. And yes this is how a site knows you have an ad blocker is installed.