CVE-2026-109434

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Fenrir Sleipnir Browser for Android before 3.9.0 contains a UI spoofing vulnerability that allows remote attackers to impersonate the browser's trusted address bar by entering fullscreen mode via the Fullscreen API without displaying a persistent notification or trusted-origin indicator. Attackers can render a counterfeit address bar showing a trusted origin over attacker-controlled content after a single user tap, enabling credential harvesting, malware delivery, or social engineering through fake login, update, or payment pages.

• www.fenrir-inc.comhttps://www.fenrir-inc.com/jp/news/2026/10/15/sleipnir-mobile-for-android-3-9-0/
• www.vulncheck.comhttps://www.vulncheck.com/advisories/sleipnir-browser-fullscreen-address-bar-spoofing