Union Pay up to 3.4.93.4.9, for android, contains a CWE-347: Improper Verification of Cryptographic Signature vulnerability, allows attackers to shop for free in merchants' websites and mobile apps, via a crafted authentication code (MAC) which is generated based on a secret key which is NULL.

References

• https://nvd.nist.gov/vuln/detail/CVE-2020-36284
• https://www.dropbox.com/s/6smwnbrp0kgsgrc/poc_code.py?dl=0
• https://www.dropbox.com/s/czbkdr73tclq2nr/UnionPay_Vulnerability_Report.txt?dl=0
• http://mobitec.ie.cuhk.edu.hk/cve_2020/