Step 1: Describe your environment
Xcode version: 11.3.1
Firebase SDK version: 6.18.0
Firebase Component: Firestore(Auth, Core, Database, Firestore, Messaging, Storage, etc)
Component version: _____
Installation method: cocoapods

Step 2: Describe the problem

There is a potentially exploitable out of memory condition In Nanopb before 0.4.1, 0.3.9.5, and 0.2.9.4. When nanopb is compiled with PB_ENABLE_MALLOC, the message to be decoded contains a repeated string, bytes or message field and realloc() runs out of memory when expanding the array nanopb can end up calling free() on a pointer value that comes from uninitialized memory. Depending on platform this can result in a crash or further memory corruption, which may be exploitable in some cases. This problem is fixed in nanopb-0.4.1, nanopb-0.3.9.5