After further review, it appears that some customers did experience a very brief impact to their user authentications during the time period when this outage occurred.
Duo utilizes many caching layers to ensure expedient access to critical data during the authentication process. Software version data is one such example of this type of data as it is read frequently, but changes infrequently. During the incident some deployments refreshed their cache for software version data and loaded erroneous data into the cache. This resulted in errors being displayed during authentication. 1,876 authentications were affected across all deployments during this outage.
We have updated our error detection to ensure that we are aware of and include any information about these types of issues moving forward. We are also making updates to our platform to ensure that this type of issue will not re-occur.