Assume someone, let’s call it Bob, with not the best intentions gets the address of one of the Alice profiles. Now, if I understand right that Delta Chat protocol is just like an encrypted-required email, I do not see a reason why Bob couldn’t send malware or a virus to Alice. Of course, a virus could affect the complete Alice’s OS, but assume Alice is cautious and do not execute anything strange.
How much easy is to any malware or whatever send to an specific profile of Alice, affect to other profiles? Could it, for example, get the addresses/links to all the profiles of Alice?
Profiles (a.k.a. accounts) are quite well separated, almost as well as running a separate instance of Delta Chat for each profile. Different profiles are controlled by the same Delta Chat Core OS process, but each profile has a separate database. Delta Chat doesn’t transfer data between profiles by itself (at least it doesn’t do it directly, but maybe something like DNS cache could be shared, I’m not sure). There are some cross-profile features, such as being able to forward message to another profile, but that requires user action.
So no, getting in contact with other Alice’s profiles should definitely not be possible for Bob.
(although if your life depends on it, you better actually run another Delta Chat instance, in a VM).