The Counter-Strike blog announces the commencement of Operation Wildfire, offering free unlimited access to seven community-created maps, the return of Nuke, and the chance for an enhanced experience through the purchase of the Operation Wildfire Access Pass. There's a separate post explaining the reintroduction of Nuke, and here are some details:

Operation Wildfire begins today, featuring unlimited FREE access to a collection of seven top-rated community maps, and the return of Nuke!

Operation Wildfire Access Pass
Want to get the most out of Operation Wildfire? With an Operation Wildfire Access Pass, you’ll gain access to a host of features.
Activate your pass, and you’ll get an Operation Journal that will track your stats in official competitive matches, along with an Operation Wildfire Coin which is displayable wherever your avatar is shown and upgradable by completing campaign Challenge Missions.