How to Clear or Disable HSTS for Chrome, Firefox and ...
https://appuals.com/how-to-clear-or-disable-hsts-for-chrome-firefox-and-internet-explorer/
Method 2: Clearing HSTS by clearing Site Preferences. Open Firefox, click the Library icon and select History > Clear Recent History.; In the Clear All History window, set the Time range to clear drop-down menu to Everything.; Next, expand the Details menu and uncheck every option except for Site Preferences.; Click the Clear Now button to clear all site preferences including the HSTS settings.
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