Forgot the password and cannot access WebSphere Application Server administrative console.

There are 2 possible methods for disabling security:

By way of wsadmin command:

1. <WAS_INSTALL_DIR>/bin/> wsadmin -conntype NONE
2. wsadmin> securityoff
3. wsadmin> exit
4. Restart the servers.
5. Enable the security from administrative console.
6. Restart the servers.

By way of manual edit of security.xml file, which is typically located in <WAS_POFILE_HOME>/config/cells<CELL_NAME> /:

1. Create a copy for security.xml file, in case you need to roll back.
2. Disable the security from the security.xml file (change the very first occurrence of... enabled="true" to enabled="false")
3. Restart the servers.
4. Enable the security from administrative console.
5. Restart the servers.

If your websphere is installed in cluster environment then you will need to change the security.xml file present in 

DMGR  ----  <WAS_HOME>/Dmgr/config/cells<CELL_NAME> /:

and all Application servers ---- <WAS_HOME>/Appsrv01/config/cells<CELL_NAME> /:

WARNING: Please use this as the last resort and make sure the server is not in the middle of processing any transactions.