No one gets it right every single time. No one. That's a completely unrealistic expectation. What you do is establish a bar, which you share with everyone who w

No one gets it right every single time. No one. That's a completely unrealistic expectation. What you do is establish a bar, which you share with everyone who will use your software. Then you evaluate your efforts against that bar. One of the keys to developing good software is hiring third-parties to conduct audits. A bug bounty program is one way to incentivize people who are already probing your software to take the next step and tell you about the bugs they find.