Web solutions designed using Bitrix Framework must not introduce any modification to the system kernel because such changes will not allow the system to update itself safely. If a system with modified kernel is updated forcedly, the whole web project may (and most likely will) become inoperative.

It is not infrequent that a hasty developer attempts to modify the system kernel to implement the desired functionality because he or she is unaware of existing event handler technology allowing to achieve the same result in a safer way.

If you cannot add the required features using event handlers, you can create a custom module which in the end will leave the system kernel untouched.

1. Use a development tool (file version and database control system) or an automated test to ensure the Bitrix Framework kernel was never modified.
2. Once the project development stage has been completed, update the kernel using the SiteUpdate system and verify that the updated system functions correctly.