Improper authorization in handler for custom URL scheme issue in "@cosme" App for Android versions prior 5.69.0 and "@cosme" App for iOS versions prior to 6.74.0 allows an attacker to lead a user to access an arbitrary website via the vulnerable App. As a result, the user may become a victim of a phishing attack.

Improper authorization in handler for custom URL scheme issue in "@cosme" App for Android versions prior 5.69.0 and "@cosme" App for iOS versions prior to 6.74.0 allows an attacker to lead a user to access an arbitrary website via the vulnerable App. As a result, the user may become a victim of a phishing attack.

"@cosme" App provided by istyle Inc. provides the function to access a requested URL using Custom URL Scheme. The App does not restrict access to the function properly (CWE-939) which may be exploited to direct the App to access any sites. Pantuhong Sorasiri of LAC Co., Ltd. reported this vulnerability to IPA. JPCERT/CC coordinated with the developer under Information Security Early Warning Partnership.