KeepassXC
https://github.com/keepassxreboot/keepassxc-browser and https://github.com/keepassxreboot/keepassxc-browser/blob/develop/keepassxc-protocol.md has some details, not sure if that's enough.
KeepassXC
Please add support for KeePass Cross-Platform Community Edition. There is no plugin/api yet but there is browser integration support which should do the job.