Warning: spoilers for Dark Crisis: Young Justice #6 are ahead!
The Dark Crisis: Young Justice miniseries drew to a close last month, and the very last pages of the last issue resolve one of Wonder Girl.
Tim Drake and Cassie Sandsmark haven't discussed their infamous kiss since it happened. In Teen Titans (Volume 3) # 37, written by Geoff Johns with art by Tony S. Daniel and Kevin Conrad, Cassie goes to the basement of Titans Tower and discovers that Tim has been attempting (and failing) to clone Conner Kent, aka Superboy. Initially, Cassie - who had dated Superboy before his death - is furious at Tim and exclaims that even if Tim could bring Conner back, he wouldn't be the same. Tim retorts that he's lost far too many people in his life, and that even if Conner isn't exactly the same, they could make him close enough. They then both it just how much they miss Conner, and in a moment of high emotion, they kiss. Cassie appears to immediately regret it and flees the basement, leaving Tim alone with Conner's memorial.
The kiss, initially published in 2006, wasn't mentioned again until 2022. In Dark Crisis: Young Justice #6, written by Meghan Fitzmartin with art by Laura Braga and Luis Guerrero, Young Justice has just tricked Mickey Mxyzptlk into a trap. As the team celebrates, Tim pulls Cassie aside and finally apologizes "for how you and I... after Conner died." The scene flashes back to Tim gazing up at a statue of Conner as he explains, "I didn't understand what I was feeling." Cassie forgives him and attributes the kiss to their relative youth at the time. She's clearly moved on and considers the kiss in the basement of Titans Tower to be just an impulsive decision made by two emotionally wrecked kids.
Robin Explains Why The Kiss Happened

DC Comics readers know now that Tim is bisexual, and that before the official confirmation, his sexuality had been alluded to for decades. Most of these allusions and teases involve Conner Kent. Conner has long been considered Tim's closest friendship, but many of Tim's actions and feelings toward Conner can be recontextualized with the knowledge that Tim is queer. Tim's confession that he didn't understand what he was feeling is placed directly over a of Tim looking up at Conner's statue. This intentional placement heavily implies that Tim kissed Cassie because he really wanted to kiss Conner instead, which would explain the feelings he wasn't sure of.
DC fans have long theorized that Tim and Conner have some sort of romantic tension between them, so this confirmation - even if it’s vague - is huge. Tim is currently in a relationship with Bernard Dowd, so Tim and Conner won't exactly be falling into each other's arms anytime soon, but it'll surely be interesting to see if DC continues to address the history between Robin and Superboy.
Dark Crisis: Young Justice #6 is available now from DC Comics.