Starting in Tiki 3, the usage of potentially dangerous plugins needs to be validated in a case by case basis. An admin can do that through tiki-plugins.php.
Then, if you go to one of those pages listed in the previous list, you'll find a box with the option to see the details to that plugin usage. Users with the required permissions will be able to preview and validate or reject them.
Example from 8.x
This example shows the "Approve all pending plugins" button. Note the Refresh button that should be used after a Tiki upgrade; that process can take a very long time to reparse all of the pages of your Tiki site; you may have to perform that Refresh more than one time to fully reparse your site.