Crayfish allows Remote Code Execution via Homarus Authorization header

Summary

Crayfish is a collection of Islandora 8 microservices, one of which, Homarus, provides FFmpeg as a microservice. Prior to Crayfish version 4.1.0, remote code execution may be possible in web-accessible installations of Homarus in certain configurations. The issue has been patched in `islandora/crayfish:4.1.0`. Some workarounds are available. The exploit requires making a request against the Homarus's `/convert` endpoint; therefore, the ability to exploit is much reduced if the microservice is not directly accessible from the Internet, so: Prevent general access from the Internet from hitting Homarus. Alternatively or additionally, configure auth in Crayfish to be more strongly required, such that requests with `Authorization` headers that do not validate are rejected before the problematic CLI interpolation occurs.