Pull Request reviewers are showing unrelated users not part of the workspace

Summary

Random users who are not part of the workspace shows up in the drop-down when trying to add a reviewer to a Pull Request. The below screenshot illustrates the problem. None of the users in the drop-down are part of the workspace.

Cause

This happens when the repository is public. The search bar for the reviewer searches globally in the entirety of Bitbucket instead of just your workspace.

Solution

You can make your repository private from Repository Settings → Repository Details → Access Level. Checking the checkbox "this repository is private" will make the repository private and will restrict the user searches in your pull request to your workspace members only.

. The below screenshot shows the setting -