Hadoop  2.7.7 Release Notes
These release notes include new developer and user-facing incompatibilities, features, and major improvements. 
Changes since Hadoop 2.7.6
-  HDFS-13602.
     Major improvement reported by Erik Krogen and fixed by Chao Sun (ha , namenode)
 Add checkOperation(WRITE) checks in FSNamesystem
 
-  HDFS-13486.
     Major bug reported by Wei-Chiu Chuang and fixed by Wei-Chiu Chuang 
 Backport HDFS-11817 (A faulty node can cause a lease leak and NPE on accessing data) to branch-2.7
 
-  HDFS-12156.
     Major bug reported by Akira Ajisaka and fixed by Akira Ajisaka (test)
 TestFSImage fails without -Pnative
 
-  HADOOP-15486.
     Major improvement reported by Nanda kumar and fixed by Nanda kumar (net)
 Make NetworkTopology#netLock fair
 
-  HADOOP-15473.
     Critical bug reported by Gabor Bota and fixed by Gabor Bota (kms)
 Configure serialFilter in KeyProvider to avoid UnrecoverableKeyException caused by JDK-8189997
 
-  HADOOP-14970.
     Minor bug reported by Erik Krogen and fixed by Erik Krogen 
 MiniHadoopClusterManager doesn't respect lack of format option