Summary

Some Assignable User Permissions allow any user to be selected in the assignee field at issue creation

Please note that this issue doesn't happen with any Assignable user Permission. For now, it has only been reproduced in the case where this permission is granted to:

• either Group custom field value
• or User custom field value

From what I observed which this type of Assignable User Configuration is that:

• on the issue creation view, the assignee field shows all users from the JIRA instance, instead of only the users who are assignable
• if we select a user who is not assignable, it is impossible to create the ticket and JIRA will complain about this user (which shows that JIRA will verify the permission AFTER the user is selected, and not BEFORE)

Steps to Reproduce

Scenario 1 (User custom field value):

Steps:

1. Create a field of type "User Picker (multiple users)""
2. Go to a project setting page, click on permission
3. Edit the permission to only grant the field created in step 1 the "Assignable User" permission
   
4. Create an issue within this project
5. Select a group in the field created in step 1
6. Click on the assignee field and notice that any user from the entire JIRA instance can be selected
   
7. Try to click on the "Create" button and notice that JIRA is displaying an error saying that the issue can't be assigned to the selected user
   

Scenario 2 (with Group custom field value):

Steps:

1. Create a field of type "Group Picker (single group)" or "Select List (single choice)"
2. Go to a project setting page, click on permission
3. Edit the permission to only grant the field created in step 1 the "Assignable User" permission
   
4. Create an issue within this project
5. Select a group in the field created in step 1
6. Click on the assignee field and notice that any user from the entire JIRA instance can be selected
   
7. Try to click on the "Create" button and notice that JIRA is displaying an error saying that the issue can't be assigned to the selected user
   

Actual Results

Non Assignable users are able to be selected in the assignee field, but if we create the issue, JIRA shows an error saying that the user can't be assigned the issue.

Expected Results

Non assignabe users should not show up in the Assignee field.

Notes

This appears to only occur during Issue Creation. If the issue has already been created, JIRA will not allow a non-assignable user to be set as the assignee.

Workaround

There is currently no workaround for this issue.