I am using Firefox 45.0 and Dependency added in pom.xml is selenium-firefox-driver 2.53.0.
pom.xml
selenium-firefox-driver 2.53.0
java.lang.NoClassDefFoundError: org/open
I ran into this too. I changed to the following and it went away.
org.seleniumhq.selenium selenium-server 4.0.0-alpha-2 io.appium java-client 6.1.0 provided