Google search results greyed out on Firefox

I logged in to my work computer today and came across this weird issue:

It's worth noting that none of these websites were visited by me.

I tried opening Firefox in Safe Mode but the issue persists. However, it goes back to normal (blue hyperlinks) when I open Firefox in Private Mode. It's also normal in other browsers.

Clearing the "Form & Search History", the Cache, "Offline Website Data" and Site Preferences has been of no avail. Restarting the computer was also ineffective.

What may have cause this, and what else can I try in order to fix it? I really wouldn't want to clear my browsing history for what appears to be a random bug.

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