The HTTP Strict-Transport-Security response header is a header used in a website to notify a browser that it should only be accessed using HTTPS, instead of using HTTP. HTTP Strict Transport Security (HSTS) header’s max-age value is lower than the recommended value. It is only set to six months. The Strict-Transport-Security header is ignored by the browser when the website is accessed using HTTP. The browser does this because an attacker may intercept HTTP connections and inject the header or remove it. If the website is accessed over HTTPS and if the website doesn’t have any certificate errors, the browser knows your site is HTTPS capable and will use the Strict-Transport-Security header.
The main impact under this vulnerability:-