Can someone working on WhatsApp weigh in on this or are there very restrictive NDA's? I would expect it's an interpretation of the TOS, so WhatsApp should be able to communicate if this is a possibility or not.
I work on a competing product (not for any of the named companies in this thread).
I don't think there is any fault with the e2e encryption. Humans are very bad at seeing causality when there is none, or accidentally leaking their thoughts into the search box.
There could also be leaks with the clipboard, photo gallery or keyboard - all things that freemium apps love to scan in the background. The way real-time-bidding ad markets work, anyone that the data leaks to can influence ad ranking - doesn't have to be FB/Meta.
If you did a true blind study, I think you'd find no link.
For example, start with a list of 1000 products images and accompanying text. Select 2 at random each day. Flip a coin to decide which to send (keep the other as control). Cover the screen so the user can't see what they've sent/received. Then, a few days later ask the user to select which product they think they sent.
I'd bet that even after months of doing this, there will be no finding of a leak.
