[firebase_auth]: java.util.ConcurrentModificationException

### [READ] Step 1: Are you in the right place?

Issues filed here should be about bugs in **the code in this repository**. If you have a general
question, need help debugging, or fall into some other category use one of these other channels:

- For general technical questions, post a question on [StackOverflow](http://stackoverflow.com/)
with the firebase tag.
- For general Firebase discussion, use the
[firebase-talk](https://groups.google.com/forum/#!forum/firebase-talk) google group.
- For help troubleshooting your application that does not fall under one of the above categories,
reach out to the personalized [Firebase support channel](https://firebase.google.com/support/).

### [REQUIRED] Step 2: Describe your environment

- Android Studio version: Android Studio Koala Feature Drop | 2024.1.2 Patch 1
Non-Bundled Plugins:
Dart (241.18968.26)
io.flutter (85.0.1)
- Firebase Component: firebase_core, firebase_auth
- Component version: 4.0.0, 6.0.0

### [REQUIRED] Step 3: Describe the problem

#### Steps to reproduce:

Issue was previously opened https://github.com/firebase/firebase-android-sdk/issues/5643 however is closed and locked now.

Please check the stacktrace below reported via firebase crashlytics.

[com.agendaboa.app_issue_2a613512125591f1195354d519518214_crash_session_68C314BB02FC00017847CA6809454AE3_DNE_0_v2_stacktrace.txt](https://github.com/user-attachments/files/22291425/com.agendaboa.app_issue_2a613512125591f1195354d519518214_crash_session_68C314BB02FC00017847CA6809454AE3_DNE_0_v2_stacktrace.txt)

Device
Brand:Motorola
Model:Moto G15
Orientation:Portrait
RAM free: 1.03 GB
Disk free: 175.02 GB
Operating System
Version:Android 15
Orientation:Portrait
Rooted: No
Crash
Date:Sep 11, 2025, 11:58:24 PM