It has been detected a sequence that could mean a hacker attack.

When inviting someone from the software for the event I get the following message on Events Booking Joomla 3:
It has been detected a sequence that could mean a hacker attack. Your request can not be processed.

Hello

Are you saying about invite friend feature? It will send emails to the people you entered, maybe your hosting provider block the request for some reasons

For this, I guess you will have to contact your hosting provider and ask them to see why that error message is received and why they do not allow the request

Base on their response, we can check it further

Tuan