samedi 10 octobre 2015

View attachments inline in html

This is a question related to an internal web site with a small user base. It is used for threaded conversations between users (like a forum), but it is all custom made and contains some business logic. Users are allowed to upload attachments. And other users see a link to these attachments in the view an can download using that link.

I want to add a new feature to display images inline, instead of showing a link. I thought about sending an image tag with source attribute set to the location of the attachment.

My problem is, this is open for XSS attacks. A user might upload a javascript file that has a png extension, and image tag will execute the javascript on resource loading.

If relevant, backend is running a python based web server and front end is mostly plain html/javascript.

What would be a correct method to prevent attacks on this system?




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