rp3-config performs inadequate parameter validation on the account name,
username and
phone number fields (possibly others) during PPP configuration.   Strings
containing characters such as < > ; & ( ) { } [ ] may be arbitrarily
written to the ifcfg-pppN files, where they will cause assorted
malfunctions when trying to use those connections.

These may be used to execute arbitrary commands as root (set account name
to foo;ls>/tmp/bar, e.g.), but since rp3-config is subject to root password
authentication, this probably isn't an issue.  It becomes one, however, if
there is any way to run rp3-config without authentication.

Proper behavior in this instance would be very rigorous escaping, or better
the deletion of any nonalphanumeric characters, in all fields.

As a possibly unrelated bug, when characters appear in the entry string
that are escaped by rp3-config on the way down to the config file, a few
characters of random gibberish may be appended to the end of the line,
suggesting a buffer problem of some persuasion.

I'll download the source and try to supply a fix.

Reproduction: repeatable.
Consequence: breaks the PPP connect by causing shell syntax errors; remote
chance of root compromise if rp3-config can be run without root-pw
authentication.
Procedure: edit an existing PPP configuration.  in account name or username
fields, enter "foo (bar)" (no quotes), or "snaf;ls>/tmp/foo" (no quotes). 
File written to ifcfg-pppN will have a form similar to the following:

DEVICE=ppp1
NAME=ISP;ls>/tmp/acctname
WVDIALSECT=ISP;ls>/tmp/acctname
MODEMPORT=/dev/ttyS0

Running usernet after something of this sort is done yields a slew of gtk
warnings.