Whether it be due to technology the site is using, or any manual behind-the-scenes work with the data, why does this breach detection site seem to be unquestioningly safe?
Wouldn't the data of you, as a user(breached/pwned or not), utilizing this tool be used against you if not secure properly(see examples below)? What is this website/project doing or using to prevent this?
If you go to this site, enter your information, you are at least providing the potential Boolean checkbox of: "Visitor [YourUsernameProvided] cares to check."
Is this not valuable data? If black hats out there have something like a list of 2,000,000, and they take/intercept the data provided by this site, couldn't they get a smaller list of 12,000? A curated list of targets that "care"? "Targets that care" can mean "Targets that have value". It can mean "Targets that are active". Perhaps even "Targets who are actually humans, not bots".
On another note, if you use the site to check multiples of your usernames, wouldn't you potentially be crafting a list of "All these usernames have been accessed from this location" and therefore be tying all your online personas together?
This all sounds like free work given to black hats. So, what technologies or methods are in place to prevent such a thing?