Are the flames too high in my oven?
Flames should not come out of the vents inside the oven. This should not be happening. It could indicate an incorrect or faulty regulator, or ventilation problems. In addition to fire, you may also be at risk of carbon monoxide poisoning.
Your oven is not safe to use. Don't use it until you can get it fixed. Since you just bought it, contact the manufacturer/reseller/installer. Hopefully those are all the same entity, in which case there will be no way they can shift the blame onto each other. Expect whoever made the mistake to leap at the opportunity fix the problem, and feel extremely lucky that they aren't being sued by your next-of-kin. (That's not to say that they actually will do that; just that you should expect it of them, and communicate that you expect it of them.) If you had it installed by an unqualified handyman, find someone more qualified to inspect and repair it.
If you installed this yourself, and/or are planning to fix it yourself, DIY Stackexchange would be a good place to look for advice.
This issue can happen if a natural gas stove is converted for use with propane, the oven wasn't adjusted to compensate for the change.

Note: AMtwo, Sneftel, mroll and Joe pretty much answered the question in the comments section, so I just summarized their comments here.