bartk

Thanks Stefano, moving to another tab before saving did the trick.

I also found deleting only the cookie “ui-tabs-1” allows access to the admin panel again after being locked out.

The site is hosted at Arvixe. I will ask them to look at their mod_security configuration.

Same problems here.
Deleting the plugin folder /easy-custom-auto-excerpt/ (by ftp or cpanel file manager) will stop the errors.