The primary danger is that a password leaked from one service might work on another (e.g., banking or social media) if the user reuses credentials.
These are standard plain-text files designed to be fed into automated tools for credential stuffing . Security risks and implications 300-K HQ-Mail-Access .txt
"HQ-Mail-Access" is common slang in hacker forums for "High Quality" mail access. This indicates the credentials (usually in email:password format) are claimed to be valid or verified for logging directly into email accounts. The primary danger is that a password leaked
The "300-K" suggests the file contains approximately 300,000 unique records . 000 unique records .