How to prevent unauthorized in-app purchases?
To prevent unauthorized purchases, you can require authentication for all purchases, including in-app purchases, made through this Google Play account on this device. This is important if you share your device with others or want to prevent purchases in kid-friendly apps. Authentication means certain information, like a password, must be entered on your device to make a purchase.
Change authentication settings on your mobile device
- Open the Google Play Store app .
- Tap Menu Settings.
- Tap Require authentication for purchases.
- Choose a setting.
- Follow the on-screen instructions.
Note: To change authentication settings you will need your Google password. Visit account recovery if you don't remember your password.
Reference: Google Play Help
Prevent in-app purchases from the App Store
- Go to Settings > Screen Time, then tap Turn on Screen Time. ...
- Tap Continue, then choose "This is My [device]" or "This is My Child's [device]." ...
- Tap Content & Privacy Restrictions. ...
- Tap iTunes & App Store Purchases.
- Tap In-app Purchases and set to Don't Allow.
Reference: Apple Website