Yappli is an application development platform which provides the function to access a requested URL using Custom URL Scheme. When Android apps are developed with Yappli versions since v7.3.6 and prior to v9.30.0, they are vulnerable to improper authorization in Custom URL Scheme handler, and may be directed to unintended sites via a specially crafted URL.

References

• https://nvd.nist.gov/vuln/detail/CVE-2021-20873
• https://jvn.jp/en/jp/JVN66422035/index.html
• https://support.yappli.co.jp/hc/ja/articles/4410249902745