A few days ago, some Mac App Store users experienced a surprise: apps that had been installed for a long time stopped working, with an unclear message that the app is corrupt and cannot be started.
Nice news (picture The Flounder).
A certificate problem… but not only
One of the reasons for this error lies in an issue of expired certificates: some of them used to sign the application code were only valid until February 6th or 7th, 2023 (there are several). Unfortunately, the error about invalid certificates is not very explicit: the system considers the application corrupt – understand “It has been changed” – and refuses to start it.
The certificate expired in February 2023 (picture of the flounder)
But various sources point out that the date output isn’t the only problem, as reported by The Flounder and TechCrunch. In the first case, it was found that applications signed with a valid certificate did not work, and in the second case an explanation is given: the fact that Apple tightened security.
According to TechCrunch, the problem comes from the nature of the signature. The firm switched to SHA-2 encryption in September when older apps used SHA-1 (notoriously weak). And obviously some old applications integrate a library that is too old to validate the new certificates, which prevents them from being replaced and therefore causing an error on startup. In theory, of course, developers can update their applications to validate certificates correctly, but this is not systematic: some apps have been abandoned over time. In this case, you can try reinstalling if the application is still available in your purchases.