The unanimous decision, by Chief Judge Wood, is Laurens v. Volvo Cars of N. America. Here's the beginning of the opinion, which sums things up quite nicely:
The idea of a theme and variations is a common one in music. It should be in law, too. Here we return to the familiar theme of a defense effort to pretermit a proposed class action by picking off the named plaintiff’s claim. Several variations on that theme have been tried and have failed. See Campbell‐Ewald Co. v. Gomez, 136 S. Ct. 663 (2016). (Rule 68 offers of judgment); Fulton Dental, LLC v. Bisco, Inc.,860 F.3d 541 (7th Cir. 2017) (Rule 67 payments to court registry). Undeterred, the defendant in the case now before us asserts that an unaccepted offer of relief before a putative plaintiff files a lawsuit deprives that plaintiff of standing. We see no reason why the timing of the offer has such a powerful effect. Black‐letter contract law states that offers do not bind recipients until they are accepted. See, e.g., ALI Restatement (Second) of Contracts § 17 (1981). Hence while the legal effect of every variation on the strategic‐mooting theme has not yet been explored, we are satisfied that an unaccepted pre‐litigation offer does not deprive a plaintiff of her day in court.
It's worth reading the whole thing.