I’m noticing a trend of sites patching the more obvious cross-site scripting vectors, such as search fields, but ignoring parameters in secondary pages, such as Ajax interfaces. Several applications in the Month of Facebook Bugs had pages for making Ajax calls or loading advertisements that were never meant to be loaded directly, yet doing so opened the door to XSS attacks. Keep in mind that any page on a given domain can access that domain’s cookies.
Yet another case in point came to my attention this week. I noticed that the technology news site Engadget had launched a redesign, and I began poking around the new site. After a little while, I came across four XSS vulnerabilities, all on the main www.engadget.com domain. I promptly reported the holes and they were silently patched in less than a day or two. Since they’ve all been fixed, I’ll list the example URIs I sent here for the record:
Previously, each one of these pages loaded the inserted script, which brings up an alert dialog containing the user’s cookies for Engadget. Kudos to the team behind Engadget for the quick fixes, and hopefully this will serve as another reminder to all developers to leave no page unchecked when evaluating security issues.
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