Mozilla
Most Firefox add-ons stopped working around May 4th 2019 when a certificate expired. Firefox requires a valid certificate chain to prevent malware. About nine hours later, Mozilla pushed a privileged add-on that injected a valid certificate into Firefox’s certificate store, creating a valid chain and unblocking add-ons. This disabled effectively all add-ons, about 15,000, and the resolution took approximately 15-21 hours for most users. Some user data was lost. Previously Mozilla posted about the technical details.
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