Information disclosure and privilege escalation via child-side checks

Improper privilege management in Mozilla Firefox and Thunderbird before 138 allows attackers to leak data or escalate privileges. The UITour actor trusts origin and permission checks performed in the child content process, so a compromised child can bypass restrictions on privileged parent-side actions. Exploitation requires prior control of a content process; exposed outcomes include sensitive-data access and privileged browser actions such as changing the default search engine.