This v3.2.2 release is a bugfix release, fixing several bugs present in the previous releases of the 3.2 branch. Additionally, this release provides a mitigation for a known remote code exploitation via the standard java object serialization mechanism. By default, serialization support for unsafe classes in the functor package is disabled and will result in an exception when either trying to serialize or de-serialize an instance of these classes. For more details, please refer to COLLECTIONS-580.

https://commons.apache.org/proper/commons-collections/release_3_2_2.html