We're running under "use strict" here, so if CGI->param's array-context
misbehaviour passes an extra non-ref parameter, it shouldn't be executed
anyway... but it's as well to be safe.
[commit message added by smcv]
CGI->param has the misfeature that it is context-sensitive, and in
particular can expand to more than one scalar in function calls.
This led to a security vulnerability in Bugzilla, and recent versions
of CGI.pm will warn when it is used in this way.
In the situations where we do want to cope with more than one parameter
of the same name, CGI->param_fetch (which always returns an
array-reference) makes the intention clearer.
[commit message added by smcv]
When CGI->param is called in list context, such as in function
parameters, it expands to all the potentially multiple values
of the parameter: for instance, if we parse query string a=b&a=c&d=e
and call func($cgi->param('a')), that's equivalent to func('b', 'c').
Most of the functions we're calling do not expect that.
I do not believe this is an exploitable security vulnerability in
ikiwiki, but it was exploitable in Bugzilla.
checksessionexpiry's signature changed from
(CGI::Session, CGI->param('sid')) to (CGI, CGI::Session) in commit
985b229b, but editpage still passed the sid as a useless third
parameter, and this was later cargo-culted into remove, rename and
recentchanges.
The intention was that signed-in users (for instance via httpauth,
passwordauth or openid) are already adequately identified, but
there's nothing to indicate who an anonymous commenter is unless
their IP address is recorded.
It appears that both the open-source and proprietary rulesets for
ModSecurity default to blacklisting requests that say they are
from libwww-perl, presumably because some script kiddies use libwww-perl
and are too inept to set a User-Agent that is "too big to blacklist",
like Chrome or the iPhone browser or something. This seems doomed to
failure but whatever.
Amitai Schlair
https://www.google.com/accounts/o8/id?id=AItOawlGzzISNi9sKsbbqyRjCZEecyypgaFV56U
openmedi
Simon McVittie
https://www.google.com/accounts/o8/id?id=AItOawk8U772S3jDrZJCO0WA5WaDLjJv5mMl6Yw
smcv
http://anastigmatix.net/
https://www.google.com/accounts/o8/id?id=AItOawlcaGfdn9Kye1Gc8aGb67PDVQW4mKbQD7E
https://www.google.com/accounts/o8/id?id=AItOawmbuZI4n1RsTe3Yeaqb5F-yhtR7a8BWEIE
https://www.google.com/accounts/o8/id?id=AItOawlobQ5j7hQVIGkwMWW3yKB_DWqthJcpnsQ