Ezra Bridger's journey throughout Star Wars Rebels has been tumultuous to say the least. Having lost his family, the boy was scraping by on his own when the Rebels crew took him in and changed his life.
As a Force-sensitive child, Ezra had a lot to learn from Kanan about the Force. Season one was about him finding out how to mold the Force to his advantage, sure, but it was more about finding out what the Force was at its core, and the way it flowed through the universe. He gradually became an official Jedi in training, a padawan learner.
This season, though, he's been skirting a turn to the dark side of the Force. It's something many young Jedi go through, a temptation to the raw power of the dark side, and Ezra, with essentially a padawan as his master (Kanan didn't truly achieve Jedi Knighthood until very late in this season, after his trials at the Jedi Temple on Lothal), is especially susceptible. His ability to easily commune with animals and creatures was looked upon by some as a bad sign - it's traditionally something people with dark side affinity have more ability to do.
So, when it was revealed that Ezra would be with "Old Master" Darth Maul in the season finale, speculation began that he would turn completely to the dark side. So what happened?
Well, Ezra, for the most part, resisted. His first real test came when Maul had the Inquisitor the Seventh Sister in a Force choke, and told Ezra to finish her. The padawan refused to strike her down when she was unarmed and vulnerable, though, failing that particular test.
Later, when Ezra had activated the Sith Temple weapon, which offered him the ability to end life anywhere in the galaxy, he didn't take it. Ezra knew, inherently, that such an ability and using it, would be crossing way over the line. He declined it instantly, knowing it was wrong, a great sign.
Then came the final shot of the episode. A Sith Holocron, a keeper of knowledge for the Sith, was taken from the Temple by Ezra, and he still had it when he'd returned to the Rebel Alliance. Sitting alone in his room in the Ghost, he meditates with the Sith Holocron in hand, his eyes glow red, and it starts to open.
Here's the problem - as Maul said earlier, only a Sith (or those who think like them) can open that Holocron. The only way Ezra can open that artifact is with Dark side energy.
So, did Ezra turn? Well, not fully - he held back a lot and resisted a lot. But in the end, he had to have tapped into that power. The real question now is what's next for the young Jedi? Ultimately, he's not a part of the original trilogy, so we know that something has to happen with Ezra before then; another Jedi being "on the board" so to speak would change the entire dynamic of Luke Skywalker and his mission, after all, especially one who had more direct training.
Season 3 Ezra will, then, be fundamentally changed. He has certainly come closer to the dark side of the Force than before. With Maul still alive and out there, the Sith Holocron opening, and his Jedi master blinded, Ezra is in trouble.