You mention password-based encryption of user private keys, do you have more information on how it's done? I can think of a famous "secret manager" that got this very wrong recently.
Also, when you have the time, consider adding a security.txt [1] to your main website so security researchers know how to report vulnerabilities.
I quickly glanced at the GitHub repository and basically couldn't find any test for example.
It'd be fine for any other startup, but this is something hosting seriously sensitive data and I feel like the focus is not right.
Any considerations about security you can share?
Feedback: the MongoDB dependency is annoying, from an enterprise (self-hosting) perspective. Due to their licencing, you can't have a managed service provider host it for you (unless that provider is Mongo itself). I have not looked into what data you store, but I can't imagine it's that schema-less at this point, so perhaps it could be possible to store in an SQL database instead? Or in PostgreSQL via its JSON support?
For anyone looking for an open source community project without business aspirations in a much simpler and easier to audit format, have a look at SecureStore. It's encrypted and versioned secrets stored alongside your code in your git repo. Cross-language, cross-platform, with native libraries for different languages/frameworks. Useable by teams big and small, up until the point you want a standalone, full-fledged secrets management server and are fine with adding that heavy network dependency to all your services.
I asked ChatGPT, but this appeared to be one of its "there-is-no-horsehead-in-Godfather" moments.
I'm the founder of the OSS project windmill [1] that, among others, separates the code logic from the management of secrets. We are in the same boat of being a small team doing too many features and hence have covered very lightly the secret management. I would love to see if we could write some integrations between our projects so that scripts and workflows could leverage advanced secret management.
[1]: https://github.com/windmill-labs/windmill