This is a warning that someone might have tried to compromise your site using the allvideoshare extension. This is not related to K2 but it could be related to the URL brackets issue.

AS per your request we have disable the mod security for your domain and now your domain is working fine. So we have enable the mod security again on the server for your domain.

If we permanently disable the mod security for your domain then it may chances for your domain will be compromised because mod security will block the infected or bad script. Regarding this kindly concern with your developer.

This is reply from my hosting support because i told them to disable security for my plugin after that everything is working fine with k2 but now they again enable them and it`s showing same issue now in my admin panel. so please give me a proper solution of this issue.

Regards,
Amit

I gave you a solution. I told you K2 was not causing this issue and in fact that was the case.

This is a server related issue, not a K2 one. Please address this issue to your hosting provider and c/p a link to this thread (the brackets in the URL). Other than this we cannot do anything about this, since it is not related to K2.

Can you know me that where i can change URL which is making this types of issue because hosting providers are saying that we are not responsible of your issues. So please try to help me to fix this issue. otherwise i have to purchases dedicated server that is very costly.

Regards,
Amit

The url cannot be changed it is a part of core K2 files.
If your hosting provider cannot setup modsecurity for your sites, then you should look for another hosting provider. PS. A 512mb VPS starts from 5$/ month.