In an abstract world where we didn't have a prior version, you'd be right. People would just know to untaint before using pack() or unpack() instead of after, and they'd do that.

As it is, perlsec says that only by using a regex or by making the scalar a hash key can you untaint it. The behavior of pack "a*", $val and pack "A*", $val used to leave the value tainted. Now it does not.

There is probably code somewhere that takes advantage of that fact, and under 5.10.0 that code is now less secure.

In reply to Re^4: pack() untaints data : bug or undocumented Perl 5.10 feature? by mr_mischief
in thread pack() untaints data : bug or undocumented Perl 5.10 feature? by mr_mischief

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