Samsung is in the process of rolling out its first Galaxy S8+ update in Europe. The new OTA includes Google's April monthly security update, which consists of fixes for 49 CVEs (Common Vulnerabilities and Exposures) found on Android and a patch for 16 issues which are specific to Samsung's Galaxy devices.
SamMobile obtained the entire changelog in Dutch, and the translated information suggests that the new update also brings improvements to the algorithms of the facial recognition feature on the S8+.
As of now, the OTA should be available for download in Germany and Belgium and is expected to reach more countries in the following days. Currently, there's no information if the patch is also released for the smaller Galaxy S8, but it's likely to follow soon as the two handsets are very similar.
If you've already received your S8+ and you'd like to check if the update has reached you, go to Settings -> Software update.