This is a not-infrequent situation. We have an announcement over the PA system any time an exchange is having technical difficulties. It doesn't happen super often, but I'd say that it happens somewhere in the world one to two times a month.

The exchanges usually bust a bunch of trades that happened right before the outage, depending on the nature of the problem. One would hope that that would be sufficient to prevent abuse for low-risk profits, but I'd probably be the last to know... What happens in Mother Russia stays in Mother Russia.