According to GNUCitizens.org, revealed that the email service of Goolge – GMail account is vulnerable to an attack that allows malicious folks to keep tabs on your e-mail traffic.
The victim visits a page while being logged into GMail. Upon execution, the page performs a multipart/form-data POST to one of the GMail interfaces and injects a filter into the victim’s filter list. In the example above, the attacker writes a filter, which simply looks for emails with attachments and forward them to an email of their choice. This filter will automatically transfer all emails matching the rule. Keep in mind that future emails will be forwarded as well. The attack will remain present for as long as the victim has the filter within their filter list, even if the initial vulnerability, which was the cause of the injection, is fixed by Google.