Why a 'Strong' Password Still Got Flagged as Compromised
A password gets flagged as compromised when it appears in a known data breach database, regardless of how strong or random it is — strength (resistance to guessing) and compromise (having been exposed and logged somewhere) are two different properties, and a technically strong password reused across multiple sites can still be compromised through a breach at any one of them.
Getting a "this password has appeared in a data breach" warning on a password that feels genuinely strong is confusing until the distinction between strength and exposure is made explicit.
Strength and compromise measure different things
Strength describes how hard a password would be to guess through brute force or pattern-based cracking, based on its length and randomness. Compromise describes whether that specific password has been exposed in a known breach and is sitting in a database attackers check against — a long, genuinely random password can still be flagged as compromised if it was reused on a site that was later breached.
Why reuse is the actual culprit
This almost always traces back to password reuse — using the same strong password across multiple accounts means a single breach at any one of those services exposes that password everywhere else it's used, regardless of how strong it originally was. The fix isn't a stronger password; it's a unique password for every account.
What to actually do about it
Change the flagged password on every account it was reused on, generate a new, unique password for each (a password manager makes this practical at scale), and enable two-factor authentication where available as an additional layer that a compromised password alone can't bypass.