Bad String pop up message

biccabong Said:

"Bad String pop up message: I keep getting this message when travelling and turning my phone back on. What is it? How do I make it stop?"

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Thank you for the screenshot:

About BadString:

There is an issue with the firmware of the iPhone. Your device (iPhone 5c) and its operating system (iOS 9) are quite obsolete (by well more than a decade).

So, what to try...

Restore your iPhone:

Restore from a backup or reset your iPhone to factory settings. Important: Back Up First: Be sure create a backup your iPhone prior to performing an update, that way you have something to restore your iPhone from, should anything go wrong afterwards. 

A. Restoring from a Backup:

Did your ever back up your iPhone with these installed? If so, back up you could back up your iPhone, and then restore it from the backup.

or...

B. Resetting to Factory Settings:

Go here: What to do Before you Sell, Give Away, or Trade in your iPhone, iPad, or iPod touch - Apple Support

biccabong Said:

"Bad String pop up message: I keep getting this message when travelling and turning my phone back on. What is it? How do I make it stop? [...]My phone is an iPhone 13 and I bought it new about a year ago"

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Thank you for the screenshot.

Restore or Reset your iPhone:

Restore from a backup or reset your iPhone to factory settings. Important: Back Up First: Be sure create a back up your iPhone prior to performing an update, that way you have something to restore your iPhone from, should anything go wrong afterwards. 

A. Restore from a Backup:

Did your ever back up your iPhone with these installed? If so, back up you could back up your iPhone, and then restore it from the backup.

or...

B. Resetting to Factory Settings:

Go here: What to do Before you Sell, Give Away, or Trade in your iPhone, iPad, or iPod touch - Apple Support