[UPSTYLE](https://attack.mitre.org/software/S1164) is a Python-based backdoor associated with exploitation of Palo Alto firewalls using CVE-2024-3400 in early 2024. [UPSTYLE](https://attack.mitre.org/software/S1164) has only been observed in relation to this exploitation activity, which involved attempted install on compromised devices by the threat actor UTA0218.(Citation: Volexity UPSTYLE 2024)(Citation: Palo Alto MidnightEclipse APR 2024)