Big documentation shortcoming: QString::arg()

[Marc Mutz]

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Hi!

Code using multiple QString::arg()'s on a string sequentially can be 
tricked into replacing the wrong parts of texts. If :arg() is used to 
insert (multiple) "user-supplied" strings, then the resulting program 
may be vulnerable to quite a few attacks. A simple test program is 
attached. Try e.g.
$ testqstring '%1 first text' 'second text'
1: s == 1: %1 first text; 2: %2
2: s == 1: second text first text; 2:

This is particularly dangerous if this mechnism is used to construct 
command lines to be executed.
Of course, a careful programmer will never use arg() for this and always 
check the to-be-inserted strings for "%n" and warn if one is found, but 
nonetheless a big fat warning in the documentation of QString::arg() 
should be in order.

Thanks,
Marc

- -- 
Marc Mutz <mutz at kde.org>
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