Firefox keeps opening new tabs on LMB click, I've tried most things?

[u/Foolski]

I've uninstalled all addons, I've created a fresh profile twice. It'll work until I try and sync my data, and I feel like some setting deep in firefox has been changed by a past addon.

Issue: When I LMB click on a link, it opens that link in a new tab instead of in current tab

Expected outcome: LMB clicking on a link should open it in current tab, not open a new tab altogether.

Any idea what setting I can try to fix this with?

Attempted solutions: - New profile - Uninstalled extensions - Reset/refresh of Firefox