Safari 8.0.7 Don't show more alerts from this webpage

In this version of Safari 8.0.7, it allows you to mute alerts from a webpage that is repeatedly showing JavaScript alerts. The JavaScript alert dialog has 2 new visible changes

1. The title now shows "From [webpage_name]"
2. A checkbox with the text “Don’t show more alerts from this webpage”

To be more precise, the checkbox with the text “Don’t show more alerts from this webpage” will only appear when a confirm or alert box is triggered multiple times. Checking the box will mute future alerts from the page. This allows you to mute alerts from pages that either accidentally show the same alert over and over, or use alerts as an attempt to prevent you from leaving the page.

When it first occurred, I got curious and decided to test out this new feature. Unfortunately there isn't a setting in the preferences of Safari to enable back the alert boxes.

After some trial and error, I found out you could enable them back by:

1. Closing all browsers on that page and loading them again
2. Clear the related website data found in the Privacy section (See screenshot below)