Safe Browsing extension

[gadabout3]

Every now and then this tab opens when I open Firefox moz-extension://16c6dc72-f053-416a-9cd5-cad3b2f3e31b/welcome.html
I can always tell when this tab is going to open as any other tabs are prevented from opening until after it's opened.

[dickvl]

moz-extension:// links are used by extensions.
To see what extension this is about, you can open the about:debugging page and look under "This Firefox" for its UUID (16c6dc72-f053-416a-9cd5-cad3b2f3e31b).