I get pink borders around everything in the latest Safari app

That usually points to an Accessibility feature being turned on, rather than a Safari problem.

I’d check System Settings > Accessibility > Keyboard > Full Keyboard Access. If it’s on, turn it off and see whether the pink outlines disappear. Full Keyboard Access shows a colored outline around whichever item currently has keyboard focus, and that color can be customized.

You can also press Option-Command-F5 to open Accessibility Shortcuts and see if anything was enabled accidentally.

Apple’s description of Full Keyboard Access is here: Change Keyboard settings for accessibility on Mac - Apple Support

Thanks for checking that. One other Accessibility setting can add colored outlines: go to System Settings > Accessibility > Hover Text and see whether Hover Text or Hover Color is turned on.

If either is enabled, try turning it off and check Safari again. Those settings can use a custom color to outline items under the pointer.

Apple explains the setting here: Change Hover Text settings for accessibility on Mac - Apple Support

Is this just in Safari? or other apps, too?

My first thought was the same as PreCognition's, but that would be system-wide, affecting all apps, not just Safari, which is why knowing the breadth of the problem is helpful.

If just Safari - all pages? or just specific ones?

Can you post a screenshot so that we all know what you're seeing?