How to fix hsts disabled on PrestaShop

Steps for PrestaShop

1. In PrestaShop Admin, go to Shop Parameters → General → Enable SSL on all pages → set to YES, and Enable SSL → YES.
2. Then set the HSTS header at the server level: for Apache, edit .htaccess in your PrestaShop root and add inside <IfModule mod_headers.c>: Header always set Strict-Transport-Security "max-age=31536000; includeSubDomains"
3. For Nginx, add add_header Strict-Transport-Security "max-age=31536000; includeSubDomains" always; to your server block and reload nginx.
4. Verify: curl -I https://yourdomain.com | grep -i strict

What is hsts disabled?

HTTP Strict-Transport-Security (HSTS) is a security header your web server sends to browsers. It tells the browser: "Never load this site over plain HTTP — always use HTTPS, no matter what." Once a browser sees this instruction, it enforces HTTPS automatically for the duration you specify (the max-age, measured in seconds). A max-age=0 effectively disables HSTS, meaning the browser forgets the rule immediately and offers no protection. The correct setting is max-age=31536000 (one year) with includeSubDomains so all parts of your site are covered.

Without a valid HSTS header, shoppers who type your domain into a browser or click a plain HTTP link are briefly exposed to a "downgrade attack" — a hacker on the same network (e.g., public Wi-Fi) can intercept that first unencrypted request and silently redirect them to a fake version of your store, stealing passwords, credit card numbers, or session cookies. This is classified under OWASP's A02:2021 Cryptographic Failures, one of the most exploited vulnerability categories in real-world breaches. Beyond security, Google has used HTTPS as a ranking signal since 2014, and browsers display "Not Secure" warnings that destroy shopper trust and conversion rates. Fixing HSTS is a free, low-effort change with immediate security and trust benefits.

See the complete Hsts disabled guide for every platform and the full background.