A better way would be avoid the external grep command - unless you want people to be able to delete all your files!

 Your code looks like this:

$ItemForm   = param('item');
$OldLine = `grep $ItemForm stock.dat`;

[download]

 Because you're not validating the input at all, (I'm suprised that the -T flag doesnt catch this), a malicious user could pass something like:

/cgi-bin/script.cgi?item=t%20/etc/passwd;%20rm%20-rf%20~;echo

[download]

 This would make your command:

`grep t /etc/passwd; rm -rf ~; cat stock.dat`

[download]

 You see the problem? ;)

Steve
---
steve.org.uk

In reply to Security problem in your code ... by skx
in thread Read/Write ASCII file by Anonymous Monk

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