alt Hacker News> The bad package version has also just disappeared from crates.io with no indication its been yanked.
So, yanked crate versions do have an indication on crates.io. (Here's an example: [1]) The Rust blog post uses the word "deleted", and I'm guessing a bit here, but I think they mean that literally, and that the version here is deleted, not yanked. And I think that would be more appropriate: a yanked crate is still downloadable by cargo, if your lockfile is locked to it already; yanking only prevents lockfiles from newly automatically acquiring a lock on that version. That wouldn't be desirable in the case of a compromised crate: you don't want a download occurring at all. The tradeoff of "break those with locks on the crate" tips to being worth it.
That said, I agree with you, though: I think this state (if it is "deleted" and not yanked) should be plainly indicated on the crate's versions page. (Even better would be if it came with a link to, e.g., the blog post or a RUSTSEC so that you could find out why.) (& I think perhaps the docs for yank should point out whether or not it is appropriate in the "compromised crate" scenario, and if not, what to do instead.)