It does appear that squeeze's libpurple0 is affected by this, though the patch doesn't apply cleanly. Technically, the possible crash is in the client code, and I don't think pidgin or finch exhibit this behavior; the original bug was against Adium for OS X, based on libpurple. I don't think backporting the patch would be too difficult, but it might be difficult to try reproducing the issue on pidgin to test that the problem would actually get fixed.
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