Thanks for the tips. I played around with passing variables to Splunk CLI using the examples you had in this post and was able to change passwords w/o exposing the password on the screen or storing the password in a file.
read -sp "Enter Current Password: " currPass
read -sp "Enter New Password: " newPass
/opt/splunk/bin/splunk edit user john -password $(echo $newPass) -auth john:$(echo $currPass)'
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