The title basically says it all. Has any actor played in both the DC Extended Universe and the Marvel Cinematic Universe? Preferably not some extra. Upcoming movies also count.
At first, this question seemed too broad to me. This list alone contains 19 actors that were in both DC and Marvel productions.
However, it seems to focus on the Marvel Cinematic Universe and the DC Extended Universe, and that's a smaller field. MCU still spans over more than 20 films and 5 TV shows, but it doesn't include anything Marvel-related prior to Iron Man (2008), and the DCEU only released 3 films so far and doesn't seem to include the DC-related TV shows (for now, anyway).
Therefore, the answer is Yes, but I can only come up with 2 actors that appeared in both universes:
1. Ayelet Zurer
DC Extended Universe: Lara Lor-Van, Man of Steel (2013)
Marvel Cinematic Universe: Vanessa Marianna, Daredevil (2015)
DC Extended Universe: Waylon Jones \ Killer Croc, Suicide Squad (2016)
Marvel Cinematic Universe: Algrim the Strong \ Kurse, Thor: The Dark World (2013)
- Australian actor Callan Mulvey was Jack Rollins in Captain America: The Winter Soldier (2014) and Anatoli Knyazev in Batman v Superman: Dawn of Justice (2016)
- Actor Scoot McNairy played Wallace Keefe in Batman v Superman: Dawn of Justice (2016) and Jackson Norriss in the one-off short All Hail the King (2014) which technically belongs in the MCU
[There could be more, though. It's a little hard to go over every actor that appeared on all the Marvel shows, and many of the upcoming films' casts aren't finalized yet.]