Apple sends out letter apologizing/explaining Mac App Store certificate issues

About a week ago, the Mac App Store came a bit off its rails, at least for some apps.

Yesterday, Apple sent out a letter of explanation and apology to developers whose apps were affected. Bottom line, this was a caching issue:

Unfortunately, a caching issue with the Mac App Store meant that some users had to restart their systems and re-authenticate with the Mac App Store to clear a system cache of some outdated certificate information. We are addressing this caching issue in an upcoming OS X update.

Also, some apps are running receipt validation code using very old versions of OpenSSL that don’t support SHA-2. We addressed this by replacing the new SHA-2 certificate with a new SHA-1 certificate last Thursday night.

Presumably, by now, the new caches are propagated, everyone has their apps back. Good to know that Apple knows the cause and that steps are in place to prevent this from happening again, at least in the same way.