Style attributes (style="") do not refer to a URI,
though any valid CSS setting for that element which
uses a URI may be used. In this case the STYLE attribute
and tag are not different.
The SRC value of an IMG tag is not the issue,
whatever type of image, the browser SHOULD
only handle it as an image. Although certain
plugins may have co-opted control of given
MIME-types (eg. QuickTime and PNG), and be exploitable.
What was likely referred to is touched upon in the
(and so many others) are allowed event attributes
such as ONLOAD which can execute inlined script.
The matter at hand is Cross Site Scripting, this
is protecting the user from malicious foreign content.
*Mis*configuration of a server to execute images
on the server is irrelevant( The only likely
means for this is to have the execution bit set
on the file on a UN*X server and allow execution
of either any file, or files by location. Files
from a Samaba share typically appear to have the
execution bit set. Again though, this affects the
perl -pew "s/\b;([mnst])/'$1/g"