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Latest Posts

Adding preventive revocation alerts to our certificate monitoring

As part of our SSL certificate monitoring, we check a lot of things. The usuals, like if it covers the right domain name or if it hasn't expired are, of course, already included. But SSL certificates can get quite complex. Sometimes, SSL certificates get revoked by the issuer. When that happens, browsers worldwide stop trusting them and will throw an invalid certificate warning.

Resolving the AddTrust External CA Root certificate expiration

Some of our users have received reports about their AddTrust External CA Root or USERTrust RSA Certification Authority certificate. The problem occurs because the remote server sends a root certificate in the chain that will expire in less than 14 days. Here are the steps to verify this and a few tips on how to resolve it.

How Oh Dear identified a certificate problem at a large CDN provider

As part of our service, we perform SSL certificate monitoring. We do this slightly different than other providers, which is why were able to detect a problem with the SSL certificates of a large, commercial, CDN provider. In this post, we'll do a technical deep-dive into how we found this problem!

Configure custom SSL certificate expiration thresholds

When we first launched Oh Dear, we had a fixed certificate expiration timer: 14 days. As soon as the expiration date came within 14 days, we'd start sending a daily reminder to hurry up and renew those certificates. Our first exception was made when Let's Encrypt gained more in popularity. We started notifying Let's Encrypt certificates 7 days before expiration date.