Hi,
Columns for country data in EventLogging tables sometimes not only contain the country code, but also larger chunks of the client cookies, which may put sensitive data into the tables.
The corresponding bug is https://bugzilla.wikimedia.org/show_bug.cgi?id=66478
At least NavigationTiming MultimediaViewerNetworkPerformance schemas for end of April 2014 onwards are affected.
If you publish reports exposing the country information/aggregates, please make sure to validate the country data against exposing sensitive information, or remove the exposing reports until the issue is fixed.
Sorry for the inconveniences, Christian