I've edited your question as we try to keep things family friendly around here. Please keep the language polite.

• Mozilla Support rules and guidelines

Do you mean the outlines for tab navigation that appear if you select a toolbar button with the keyboard?

• https://support.mozilla.org/en-US/kb/access-toolbar-functions-using-keyboard

You can set this pref to false in about:config to disable this accessibility feature.

• about:config => browser.toolbars.keyboard_navigation => false
• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

Can you attach a screenshot if you mean something different?

• https://support.mozilla.org/en-US/kb/how-do-i-create-screenshot-my-problem
• use a compressed image type like PNG or JPG to save the screenshot

I've seen another question that has a screenshot attached, so this looks like some accessibility feature that somehow got activated.

• /questions/1462306 How do I remove these new outlines of the toolbar icons?

I'm not sure if this is a Windows feature as I'm not seeing this on Linux.

After the recent firefox update windows high contrast causes this. I am assuming something changed or was added to turn on when high contrast is also on.

Thanks for reporting that. this is high contrast related. I had thought about this as a possible cause, so thanks for confirming this.