You see the headlines: “App discovered to be spying on you,” or “App removed from the store because it was downloading private information.”
Delete your third-party apps. You can always reinstall them if you decide to use them. Your phone and tablet are more secure the fewer apps you have. Most people only use 20% of their apps.
On an iPhone, press on the app’s icon and hold your finger down. Follow the prompts to remove and delete the app.
In Android, there are a few ways to delete apps as described in this article: https://www.lifewire.com/delete-apps-on-android-phone-5271421
Please forward this to your friends, so they know to delete old applications too. If they’re waiting for something anyway, it will make the time pass quicker, and they’ll be more secure.