If the leaker visits this page before opening the Tor Browser from a regular browser to copy the onion url, the whole thing is as safe as SSL as there will be a trail of the SSL connection just before the visit to SecureDrop. And they don't even explain to avoid it. OPSEC is hard.
(Securedrop dev here) This is a really good point. Unfortunately, we're "as safe as SSL" no matter what, unless the source has a separate way to verify the .onion address on the SSL-protected page. They can use the SecureDrop directory for that (and we're working on other schemes as well), but it's not automated so only a handful of very cautious sources would likely do this. I'm not sure how we could explain to avoi…
This may be one of the rare cases where the use of a QR Code is justified.