QtWeb 3.0 Builds 001 and 003 does not properly block javascript: and data: URIs in Refresh and Location headers in HTTP responses which allows remote attackers to conduct cross-site scripting (XSS) attacks via vectors related to (1) injecting a Refresh header that contains a javascript: URI (2) entering a javascript: URI when specifying the content of a Refresh header (3) injecting a Refresh header that contains JavaScript sequences in a data:text/html URI (4) entering a data:text/html URI with JavaScript sequences when specifying the content of a Refresh header (5) injecting a Location header that contains JavaScript sequences in a data:text/html URI or (6) entering a data:text/html URI with JavaScript sequences when specifying the content of a Location header.