Let's see whether .svg is supported:
Yeah, that rocks!
(Might be you will have to scroll down)
Let's see whether .svg can be uploaded to Media:
Damned, that does not work:
My conclusion
AFAIK .svg was not supported in FP 1.3, and so in was ok that Uploader refused to accept images.svg
But FP 1.5.1 DOES support images.svg, so I think those "security concerns" are a bug.