Seems like the teaser trailer leaked online, and up onto YouTube, though it has since been removed by Warner Broth­ers because of copy­right issues. To be hon­est, there’s not much to see, just some streams of light.

Here is the transcript:

Bruce: “I knew the mob wouldn’t go down with­out a fight. But this is dif­fer­ent. They crossed the line.“
Alfred: “You crossed the line first, sir. You ham­mered them. And in their des­per­a­tion, they turned to a man they didn’t fully under­stand. Some men aren’t look­ing for any­thing log­i­cal. They can’t be bought, bul­lied, rea­soned, or nego­ti­ated with. Some men just want to watch the world burn.“
Joker: Start­ing tonight, peo­ple will die. I’m a man of my word. [Laugh]