SymptomsBlank page is shown when login to Horde Webmail.
CauseOthers does not have read permissions to file /etc/passwd.
You may check permissions with command "ls -l".
~# ls -l /etc/passwd
-rw------- 1 root root 7616 Apr 7 11:04 /etc/passwd
ResolutionIt is normal for others to have read permissions to file /etc/passwd, this does not have any security risk.
Passwords of system users are stored in file /etc/shadow that have permissions -r-------- by default (only read permisisons for root).
To resolve the problem you should allow others to read file /etc/passwd. You may do that with the following command:
~# chmod o+r /etc/passwd