Previously Mozilla and Google could not reach a deal with default search engine in FF. Bing was supposed to replace google in firefox, but ultimately they have reached an agreement.

From softpedia

Everyone can relax now, Google and Mozilla have announced that they've reached an agreement over the Firefox search deal, ensuring that Google remains the default search engine in Firefox in most countries for three more years and ensuring that Mozilla has the money to continue to develop and improve its browser.

The previous deal ended in November and, when
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about it, it became "obvious" that such a deal was never going to happen and that
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.
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