Security issues with this Addon Rated 1 out of 5 stars
Security Issues founded with your Addon: http://www.breakthesecurity.com/2012/11/how-to-upload-shell-via-tamper-data-hack.html#more
The linked article documents how to break into a site using TamperData, NOT a security flaw in TamperData.
The exploit described is exactly the kind of fault in security coding that TamperData, and a good security testing plan is designed to help detect. Proper security testing, which a tool like TamperData can be part of, should be a part of the dev/qa cycle for exactly this reason.
TamperData is a testing tool, not a hacking tool, but this article is evidence that, like all tools, it can be misused. I don't support this.