I'm really sorry, but I'm the one who just broke it :S

I was leaving a friendly message on other people's todo lists to expose a vulnerability, but somehow I ended up breaking it completely, and I regret that now.

Please see this as construcive feedback. The vulnerability I was exploiting was an insecure direct object reference (https://cheatsheetseries.owasp.org/cheatsheets/Insecure_Dire...), but there are many other vulnerabilities there too, like Cross Site Scripting (https://cheatsheetseries.owasp.org/cheatsheets/Cross_Site_Sc...)

Again, I'm really sorry to break your application, but I'm more than happy to help fix the vulnerabilities - is the application open source anywhere?