In-app browser of social media is spying on you

iOS Apps that have their own In-App Browser, but what does it do with your privacy? Does the app:

– provide a button to open the currently shown link in the default browser?
– inject JavaScript code into third party websites to modify its content? This includes adding tracking code (like inputs, text selections, taps, etc.), injecting external JavaScript files, as well as creating new HTML elements.
– run JavaScript code to fetch website metadata? This is a harmless thing to do, and doesn’t cause any real security or privacy risks.
– have a link to the JavaScript code? The code might not be a 100% accurate representation of all JS commands.