Cert Reminder от truyensex

CertReminder is a reliable Firefox extension that ensures you never miss a certificate expiration. It constantly reminds you of the number of days left until website certificates expire by displaying the count on a padlock icon in the toolbar.

When there are fewer than 29 days left, the icon turns red, prompting you to take action promptly. Moreover, if the site connection is not encrypted, it shows an unlocked red padlock, signaling potential security risks.