On 1 January 2012 08:48, Michael Quinion <[log in to unmask]> wrote:
> Is it possible to set LISTSERV to require confirmation for UNSUBSCRIBE
> requests sent via such a form?

Yes - you need to change the list configuration (the "List Header"),
specifically the Validate keyword.  I would suggest you want:
 Validate= Yes, Confirm

This help is taken from the manual here
http://www.lsoft.com/manuals/16.0/listkeyw.html

     "Validate= No": all commands except PUT are taken at face value
with no validation. While users are not bothered with validation
requests, the list is almost totally unprotected from attacks by
hackers. For compatibility reasons, this is the default setting.

     "Validate= Yes": "protected" commands, such as DELETE or ADD,
require password validation. For list owner commands, personal
passwords set with the PW ADD command are accepted. Some user commands
may accept a personal password, while others will cause the request to
be forwarded to the list owners for verification. Other "protected"
commands include GET, but do not include SUB or SET.

     "Validate= Yes,Confirm": protected commands are validated using
the "OK" mechanism by default, although personal passwords are also
accepted where appropriate. This is a good compromise between list
security and list owner convenience.

     "Validate= Yes,Confirm,NoPW": protected commands are always
validated using the "OK" mechanism. Passwords are not accepted, as
they are not as safe as "cookies". This is the recommended setting for
secure lists. Note that lists with this setting cannot be managed via
the Web Management Interface.

     "Validate= All,Confirm": all commands causing a change in state,
except the PUT command (which is always password-validated), are
validated using the "OK" mechanism by default, although personal
passwords are also accepted where appropriate. "Protected" commands
(see above) are included in the class of commands that cause a change
of state. Non-"protected" commands that cause a change in state
include SUB and SET.

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