CVE-2024-9398

CVE-2024-9398 is a medium-severity vulnerability affecting Mozilla Firefox, Firefox ESR, and Thunderbird versions prior to 131 and 128.3, respectively. It allows an attacker to determine if a specific application is installed on a user's system by observing the results of window.open calls with custom protocol handlers. The CVSS score is 5.3 (MEDIUM), indicating a network-based attack with low complexity, requiring no user interaction, and potentially leading to low confidentiality impact (information disclosure). There is currently no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or inclusion in CISA's KEV catalog, though it has received limited community discussion and media coverage.