In line with the latest security impositions, most popular browsers like Chrome and Firefox are configured to recognize and access only those websites that hold a valid TLS/SSL certificate. Before it displays the requested website, the browser checks if the website has a valid certificate through a mechanism called TLS/SSL handshake. If your website’s certificate has expired, the browser no longer trusts that website.
It displays a message like “Your connection is not private” or “This site is not secure” and withholds the intended website from displaying. This essentially means your site is down, and it stays down for the whole period till the certificate is renewed, unless you find a way for your users to bypass the error. If you are a public-facing organization whose websites get a million visitors a day, even a few minutes of downtime can cause significant losses in terms of revenue, customer trust, and brand damage.
Since TLS/SSL certificates facilitate encryption of data in transit, expired certificates also leave networks prone to attacks. A network is made up of interconnected points, and even if one of those points malfunctions, the entire infrastructure collapses. If the keys are compromised as well, attackers can decrypt all the confidential data that pass through the network, which may include credit card details, user passwords, account numbers, etc.
Some of the major network outages and data breaches in the world have been caused by expired certificates. Organizations like LinkedIn, Sony Ericsson, Equifax, and many more have had certificates expiring on them, leading to worldwide outages, large-scale data breaches, and debilitating losses.