I don't think I have any ugly code but I have built insecure apps and sites before. I've asked myself "what if someone does X, could they steal data?" numerous

I don't think I have any ugly code but I have built insecure apps and sites before. I've asked myself "what if someone does X, could they steal data?" numerous times after a project is out of my hands. Similar question: How much damage could you do (or data could be stolen) by hacking sites / apps that you built in the past? My former boss, who was also a software developer, frequently told me that moving to the next project was more important than doing a thorough security audit of large public sites we built. It wasn't my company on the line, so I had no choice. Also, many of the projects I've built have been proof-of-concepts in my mind that have been rushed into production. Those projects have likely not scaled too well...