I realize that this may be more of an opinion type question, but I see a lot of questions on ethics in this forum so I hope mine fits in.
I was reading a BBC article about Heartbleed, and in the article it references couple of sites that can test other websites for presence of Heartbleed vulnerability. The sites' stated purpose is to help users see if a site that they use is currently vulnerable (e.g. test if the site I'm about to purchase from is vulnerable to Heartbleed), which in itself is a good thing.
However, they're essentially sending an attack against a target for which they have not obtained a permission to do pentesting (since any user can test any site they wish). Does this not, by itself, violate ethical boundaries?