Mozilla removed Yahoo as default search provider, retuning to Google when it launched Firefox Quantum.
It seems Oath, owned by Verizon, Yahoo's owners, decided to file a complaint against Mozilla alleging breach of contract.
There's a wordy response from Mozilla on its blog where it responds by counter-suing saying that it, "exercised our contractual right to terminate the agreement and entered into an agreement with another provider."
[
blog.mozilla.org...]
