If you cover up security incidents you are facing some actual jail time not just civic suits. Look at what happened with former uber ciso for example of this [0]

[0] - https://www.justice.gov/usao-ndca/pr/former-chief-security-o...

I think this was likely a case of a TA getting in with legitimate creds that they obtained from an outside source. How can that be stopped? Happens every day. As someone said earlier - scrub your HAR files and don't leave sensitive data out there. I don't see that this was much of a compromise of a system in that the TA likely got in with legit creds. Where these creds came from is the bigger question.

I strongly suspect a lot of organizations cover up security incidents. Also, remember that the worst organizations don’t even know they were hacked.