Missing Strict-Transport-Security (HSTS) header

What does this mean?

Without this header (HSTS), a visitor's first connection to your site could be silently downgraded from HTTPS to plain HTTP, exposing anything they submit — passwords, payment details — to interception.

What are the potential impacts?

• A visitor on public wifi — a coffee shop, airport, or hotel — can be silently downgraded to an unencrypted connection by anyone else on that network, exposing anything they type.
• This is exactly the setup used in "man-in-the-middle" attacks, where an attacker intercepts a login or payment form and captures the data before it ever reaches your real server.
• Even a single unprotected first visit is enough — HSTS exists specifically to close that gap, and its absence is invisible to visitors until it's exploited.
• For an e-commerce or SaaS site, this can mean stolen customer credentials or payment details, with the liability and cleanup cost falling on you, not the attacker.