We just upgraded our Jenkins version from "1.424.6" "1.447.1".

After the upgrade, all system groovy scripts that contained the following line stopped working:
AbstractBuild g_currentBuild = (AbstractBuild)Thread.currentThread().executable;

When this line in the script is executed, the following stacktrace was generated:
FATAL: null
java.lang.StackOverflowError
at org.codehaus.groovy.ast.ClassNode.redirect(ClassNode.java:178)
at org.codehaus.groovy.ast.ClassNode.equals(ClassNode.java:677)
at org.codehaus.groovy.ast.ClassNode.genericTypeAsString(ClassNode.java:1149)
at org.codehaus.groovy.ast.ClassNode.toString(ClassNode.java:1127)
at org.codehaus.groovy.ast.ClassNode.toString(ClassNode.java:1132)
at org.codehaus.groovy.ast.ClassNode.genericTypeAsString(ClassNode.java:1152)
at org.codehaus.groovy.ast.ClassNode.toString(ClassNode.java:1127)
at org.codehaus.groovy.ast.ClassNode.toString(ClassNode.java:1132)
at org.codehaus.groovy.ast.ClassNode.genericTypeAsString(ClassNode.java:1152)
at org.codehaus.groovy.ast.ClassNode.toString(ClassNode.java:1127)
at org.codehaus.groovy.ast.ClassNode.toString(ClassNode.java:1132)
at org.codehaus.groovy.ast.ClassNode.genericTypeAsString(ClassNode.java:1152)
at org.codehaus.groovy.ast.ClassNode.toString(ClassNode.java:1127)
at org.codehaus.groovy.ast.ClassNode.toString(ClassNode.java:1132)
at org.codehaus.groovy.ast.ClassNode.genericTypeAsString(ClassNode.java:1152)
at org.codehaus.groovy.ast.ClassNode.toString(ClassNode.java:1127)
at org.codehaus.groovy.ast.ClassNode.toString(ClassNode.java:1132)
at org.codehaus.groovy.ast.ClassNode.genericTypeAsString(ClassNode.java:1152)
at org.codehaus.groovy.ast.ClassNode.toString(ClassNode.java:1127)
at org.codehaus.groovy.ast.ClassNode.toString(ClassNode.java:1132)
at org.codehaus.groovy.ast.ClassNode.genericTypeAsString(ClassNode.java:1152)
at org.codehaus.groovy.ast.ClassNode.toString(ClassNode.java:1127)
at org.codehaus.groovy.ast.ClassNode.toString(ClassNode.java:1132)
at org.codehaus.groovy.ast.ClassNode.genericTypeAsString(ClassNode.java:1152)
at org.codehaus.groovy.ast.ClassNode.toString(ClassNode.java:1127)
at org.codehaus.groovy.ast.ClassNode.toString(ClassNode.java:1132)
[...repeats until stack overflow.]

We upgraded our Groovy plugin to the latest version (1.12) with the same result.

We rolled back to Jenkins 1.424.6 and we do not see the error there.