The child frames in Opera 9 before 9.20 inherit the default charset from the parent window when a charset is not specified in an HTTP Content-Type header or META tag, which allows remote attackers to conduct cross-site scripting (XSS) attacks, as demonstrated using the UTF-7 character set.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.008
EPSS Ranking 73.2%