This is not so much a problem as it is a query. I have enrolled onto the early access CA and since doing so have seen that the logging in process is the same (magic email link). This led me to wonder whether there is any additional check happening behind this link.
If not this means that my money will only ever be as secure as my email address. With emails turning up related to Monzo, a hacker, with access to my emails, could see thee and download the app to request their own magic link.
When using the beta pre-paid Monzo card this was not so much of an issue as someone would also require their own Monzo account to transfer funds to. However, now with real bank transfers this is slightly concerning.
Obviously, I do not expect your security features to be outlined as a response to this post. Could you please respond stating whether this thinking is correct or not, before I commit to transferring my salary into the CA.