How secure is the site privacy wise. Can it be confirmed that the site isn't storing the email addresses input into their system and probably selling them to third parties to be used for email marketing.
As far as I know, Ihavebeenpwned isn't storing email addresses searched for on their website. I got this from their FAQs section 👇.
How do I know the site isn't just harvesting searched email addresses?
You don't, but it's not. The site is simply intended to be a free service for people to assess risk in relation to their account being caught up in a breach. As with any website, if you're concerned about the intent or security, don't use it.
Thank you. I didn't know about Mozilla Monitor service until you mentioned it. I've added it to OP as it serves same purpose and it'll come in handy for users who are concerned about their privacy with Ihavebeenpwned site since Mozilla is a known organization.