Apple provided an update for older devices which could not be updated to iOS/iPadOS 15. This update fixes security issues in WebKit and recommended for all users.
Apple Support: About the security content of iOS 12.5.6
Reference: Apple Releases iOS 12.5.6 Update for Older iPhones and iPads With Vulnerability Fixes
Recommendations
Developer:
Check the update for compatibility issues.QA engineer:
Check the update for regressions.PM/DM:
Business as usual.