Reflected XSS on error page on https://apps.topcoder.com/wiki/plugins/socialbookmarking/updatebookmark.action

How it was found

Hi :) In https://apps.topcoder.com/wiki/plugins/socialbookmarking/updatebookmark.action bookmarkPageId parameter expects a number value. If you add XSS payload instead of number, an error page displays with XSS.

PoC https://apps.topcoder.com/wiki/plugins/socialbookmarking/updatebookmark.action?bookmarkPageId="><img src=x onerror=alert(document.domain)> {F816846}

Impact

XSS can use to steal cookies or to run arbitrary code on victim's browser.