Opera 9.21 allows remote attackers to spoof the data: URI scheme in the address bar via a long URI with trailing whitespace, which prevents the beginning of the URI from being displayed.
https://exchange.xforce.ibmcloud.com/vulnerabilities/35430
http://www.vupen.com/english/advisories/2007/2537
http://www.securitytracker.com/id?1018397
http://www.securityfocus.com/bid/24917
http://www.securityfocus.com/archive/1/473782/100/0/threaded
http://www.securityfocus.com/archive/1/473703/100/0/threaded
http://www.novell.com/linux/security/advisories/2007_15_sr.html
http://securityreason.com/securityalert/2891
http://security.gentoo.org/glsa/glsa-200708-17.xml
http://secunia.com/advisories/26545