Re: Hotmail security hole - injecting JavaScript using <IMG

From: Henrik Nordstrom (hnoat_private)
Date: Tue Jan 04 2000 - 16:25:02 PST

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    Kevin Hecht wrote:
    
    > While Hotmail obviously has a filtering hole, should the browser
    > manufacturers be on the hook here as well, given that javascript: URLs
    > probably shouldn't be rendered at all by the <IMG> tag?
    
    JavaScript can be used to calculate the URL to open in a IMG tag.
    
    <IMG SRC="&{find_image_to_open()};">
    n
    What is more suprising is why it is so hard to make a JavaScript
    scrubber filter. The ways javascript may be inserted in HTML is generic,
    and not tied to any specific tag or attributes. (see Netscape JavaScript
    client guide, chapter 9)
    
    <script>
    </script>
    
    <tag attribute="&{javascript_code};">
    
    <tag url_attribute="javascript:javascript_code">
    
    Due to the open nature of HTML it is impossible to know all attributes
    which may contain URLs. And I thinks it is safe to assume that all
    attribute values may be contain URLs... I can't come up with a practical
    HTML application where the attribute value "javascript:<something>"
    makes much sense other than when refering to javascript code to be
    executed.
    
    
    --
    Henrik Nordstrom
    



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