source: https://www.securityfocus.com/bid/23349/info Firebug is prone to a script-code-injection vulnerability because it fails to adequately escape user-supplied data. An attacker can exploit this issue to execute arbitrary script code in the context of the application. Versions prior to 1.04 are vulnerable. Firebug console HTML injection

Firebug console HTML injection

Cheers, Thor Larholm