Moderate vulnerability in argentinean ARNET isp webmail.

well, there is some kind of weakened authentication on the webmail 
of Arnet
(webmail.arnet.com.ar) to access any account all you need is to 
guess the first 8 characters of the password, even if the password 
is 9,10,11,12,14 or more characters long. This password is the same 
than ADSL access acount.

for example:

For this account
johndoe@arnet.com.ar
password:a1a2a3a4a5a6a7a8a9a0

you only need (first 8 character)

johndoe@arnet.com.ar
password:a1a2a3a4

ADSL account in this case is

Name: johndoe@arnet
Password:a1a2a3a4a5a6a7a8a9a0

there are no anti bruteforce mecanism so you can guess almost any 
account within a couple of hours.