Some people in this thread are claiming the article doesn’t mention Facebook.
I actually read the article. You’re welcome.
When you click on a link in the Facebook or Instagram apps, the website loads in a special browser built into the app, rather than your phone’s default browser. In 2022, privacy researcher Felix Krause found that Meta injects special “keylogging” JavaScript onto the website you’re visiting that allows the company to monitor everything you type and tap on, including passwords. Other apps including TikTok do the same thing.
Edit: The article Proton got their info from.
Better than any proprietary scanning software I’ve worked with. Highly recommend.