[nationcrafting]

>and the company actually listens to them.

So far, Telegram have been listening a lot to people pointing out errors, and fixed their errors promptly.

>for free and point it out to them? Forget about it.

It doesn't appear to be for free: aside from their bounty program, Telegram have been rewarding various troubleshooters with pretty decent ex gratia payments in bitcoin. In the article linked to this title, the first comment was from Telegram, asking the author to contact them for a reward.

[aioprisan]

They haven't been transparent about the amounts nor about the parameters of the initial bounty, which does not mean that the algorithm is safe, but rather that it wouldn't be worth the reward in effort to expose a vulnerability in the exact specified way by the authors.