Starting today, Google’s OpenRTB implementation will be updated to only include fields and messages for the latest supported version, OpenRTB 2.5 . This will affect the OpenRTB protocol and any APIs or tools used to configure bidder endpoints.OpenRTB protocol changes 
  BidRequest.imp[].banner.hmaxBidRequest.imp[].banner.hminBidRequest.imp[].banner.wmaxBidRequest.imp[].banner.wmin 
Additionally, the following fields may now be populated for all bidders:
  BidRequest.device.ext.user_agent_dataBidRequest.device.geo.accuracyBidRequest.device.geo.utcoffsetBidRequest.imp[].banner.api: This will support the value MRAID_3.BidRequest.imp[].banner.formatBidRequest.imp[].banner.vcmBidRequest.imp[].metricBidRequest.imp[].native.api: This will support the value MRAID_3.BidRequest.imp[].video.api: This will support the value MRAID_3.BidRequest.imp[].video.companionad.apiBidRequest.imp[].video.companionad.formatBidRequest.imp[].video.companionad.vcmBidRequest.imp[].video.linearityBidRequest.imp[].video.maxdurationBidRequest.imp[].video.placementBidRequest.imp[].video.playbackendBidRequest.imp[].video.skipBidRequest.site.mobileBidRequest.testBidRequest.wlang 
If a newer OpenRTB specification is published, Google may upgrade the current supported version to match it. Previously deprecated fields that are removed from the specification will also be removed from the protocol. Non-deprecated fields that are removed will be marked as deprecated in the protocol, and eventually removed following a brief deprecation period.Authorized Buyers Real-time Bidding API changes bidders.endpointsbidProtocol will be deprecated:
  OPENRTB_2_2OPENRTB_2_3OPENRTB_PROTOBUF_2_3OPENRTB_2_4OPENRTB_PROTOBUF_2_4OPENRTB_2_5OPENRTB_PROTOBUF_2_5 
New enum values for bidProtocol will be added to represent the latest supported OpenRTB version in either JSON or Protobuf formats:
  OPENRTB_JSONOPENRTB_PROTOBUF 
If you have existing endpoints with their bidProtocol set to any of the deprecated values above, they will automatically be migrated to either OPENRTB_JSON or OPENRTB_PROTOBUF depending on the format specified by the original value. Additionally, any modifications to your endpoints that would set bidProtocol to the deprecated values will instead set it to OPENRTB_JSON or OPENRTB_PROTOBUF.Authorized Buyers API support forum  with any feedback or questions you may have related to these changes.