I am interested in UX perspective for the following case. I have a web form with javascript validation and backend validation in Java.
Theoretically, if JS passes, backend validation should also pass, but in practice, sometimes, it is not the case (malicious users, hacks or just programmatic error).
What is the best way to inform the user that validation in backend have not passed?
Does it make sense at all to explain it for the user or enough just to alert him aka "Oops, smth went wrong.."?
Any other ideas?
Thank you!