I started getting these errors inside a Maven build, after the upgrade to 2.3:

ERROR: Processing failed due to a bug in the code. Please report this to jenkinsci-users@googlegroups.com
java.lang.ClassCastException: org.acegisecurity.providers.UsernamePasswordAuthenticationToken cannot be cast to org.jenkinsci.plugins.BitbucketAuthenticationToken
at org.jenkinsci.plugins.BitbucketSecurityRealm.loadUserByUsername(BitbucketSecurityRealm.java:162)
at hudson.model.User$UserIDCanonicalIdResolver.resolveCanonicalId(User.java:1048)
at hudson.model.User.get(User.java:394)
at hudson.model.User.get(User.java:363)
at hudson.plugins.git.GitChangeSet.findOrCreateUser(GitChangeSet.java:374)
at hudson.plugins.git.GitChangeSet.getAuthor(GitChangeSet.java:435)
at hudson.model.AbstractBuild.getCulprits(AbstractBuild.java:350)
at hudson.maven.reporters.MavenMailer.end(MavenMailer.java:72)
at hudson.maven.AbstractMavenBuilder.end(AbstractMavenBuilder.java:104)
at hudson.maven.MavenModuleSetBuild$MavenModuleSetBuildExecution.doRun(MavenModuleSetBuild.java:859)
at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:534)
at hudson.model.Run.execute(Run.java:1738)
at hudson.maven.MavenModuleSetBuild.run(MavenModuleSetBuild.java:531)
at hudson.model.ResourceController.execute(ResourceController.java:98)
at hudson.model.Executor.run(Executor.java:410)
project=hudson.maven.MavenModuleSet@1d9d1d07[BUILD_integration_tests]