Starting with 20:00 UTC (3:00pm US EST), today (March 4), the non-profit certificate authority Let’s Encrypt will begin it’s effort to revoke a little over 3 million TLS/SSL certificates that it issued while a bug affected its CA software. Preliminary investigation suggests the bug was introduced on July 25, 2019, but a more detailed investigation is under way – though, for now, it seems that “it’s not likely that there was any significant mis-issuance as a result of this incident.” Nevertheless, affected certificate owners have been urged to renew and replace their certificate(s) so that their sites don’t end up showing this type of alert to visitors:

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