A player in adventure mode can put out a lit candle by right-clicking on it. I expected that adventure players would not be able to alter the world similar to how they cannot toggle redstone dust (MC-184778) or dye signs (MC-138580).
MC-222818 You can ignite TNT in adventure mode
MC-138580 Adventure mode does not prevent dyeing signs
MC-184778 Redstone dust can be toggled between cross and dot in adventure mode
MC-255140 Cake can be eaten in adventure mode