1. Find the Source of the Problem and Fix It
Just because a data breach has occurred and a cybersecurity incident has been discovered, it doesn’t mean the threat has passed or that your systems are now secure. As soon as humanly possible, your IT professionals (and perhaps a hired expert, depending on the staff working at your business) need to be able to track down the source of the problem. This is less to place blame in the event of human error (which likely was involved), and more to cut off the breach and prevent the exploit from being used again in the future.
Once the problem is found, professionals should fix it as soon as possible, either by patching it or removing it (depending on the problem). In addition, the business should make efforts to ensure similar problems aren’t extant in other business systems or processes.