The beforepaste, beforecut and beforecopy events get fired when clicking the "Edit" menu in Safari. Some of these events get fired even more than once. The provided URL demonstrates the problem.
Created attachment 48645 [details] Test page
*** Bug 77630 has been marked as a duplicate of this bug. ***
I am able to reproduce this bug in Safari Technology Preview 153 using attached test case, when I have Safari open and try to click "Edit" menu from the top bar, it triggers: beforeoncut, beforeoncopy and beforeonpaste dialog boxes while no other browser like Chrome Canary 107 and Firefox Nightly 106 trigger this based on the user interaction with the OS layer controls.
<rdar://problem/100126511>