Security researchers have illustrated a new app-in-the-middle attack that could allow a malicious app installed on your iOS device to steal sensitive information from other apps by exploiting certain implementations of CustomBy default on Apple’s iOS operating system, every app runs inside a sandbox of its own. Apple offers some methods that facilitate sending and receiving very limited data between applications. One such mechanism is called URL Scheme, also known as Deep Linking, that allows developers to let users launch their apps through URLs.
Source: https://thehackernews.com/2019/07/ios-custom-url-scheme.html