Symantec took one of their widely trusted root certificates and declared that it was now "off the reservation", meaning they may choose to not comply with the BRs for its leaf certificates.
I don't know if they have actively used it to issue SHA-1 certificates, but they certainly could.
The exception process used by payment processors such as First Data were for SHA-1 certificates chaining to a root that was still publicly-trusted. They couldn't use an off-reservation root because their client devices didn't trust them.
I may be being a bit dense, but if your client device contains a root that goes off-reservation, how does it ever receive a revocation notice? Doesn't everything that chains to that root via a valid chain still get trusted?
Side note: Are payment systems required to link to revalidate their roots at any regular intervals?
> I may be being a bit dense, but if your client device contains a root that goes off-reservation, how does it ever receive a revocation notice? Doesn't everything that chains to that root via a valid chain still get trusted?
Yes, if a client isn't receiving root store updates it will continue to trust certificates chaining to the off-reservation root. This is why taking previously-trusted roots off-reservation is bad for the ecosystem and would ideally be prohibited.
> Side note: Are payment systems required to link to revalidate their roots at any regular intervals?
Many payment systems apparently have no automatic update mechanism, so I assume there is no requirement for such.
Indeed, I was just speculating that more banks and payment processors might take advantage of the off-reservation root if it was possible, given the type of companies that publicly showed they needed one.
I don't know if they have actively used it to issue SHA-1 certificates, but they certainly could.