I created a custom login page which is actually a login form which is a lightning component and this uses an apex controller(class). I have also given user's profile access to apex controller(class). Also tried by using 'with sharing' and 'without sharing' keywords for class, but still getting the error:
Error message: You do not have access to the Apex class named 'MyApexController'
When I deactivated the critical update it is working fine. But when I activate it again it is not working. Please Help..!!

I created a custom login page which is actually a login form which is a lightning component and this uses an apex controller(class). I have also given user's profile access to apex controller(class). Also tried by using 'with sharing' and 'without sharing' keywords for class, but still getting the error:
Error message: You do not have access to the Apex class named 'MyApexController'
When I deactivated the critical update it is working fine. But when I activate it again it is not working. Please Help..!!

Requirment: 
Salesforce Org A : will publish event when a Case is been updated.

Salesforce Org B : Case information sent as event message will be consumed in this org and certain business action are trigger based on the Case info.

What is the Apex Code / Configuration on Salesforce Org B to subscribe for the event and consume events ?