diff --git a/x-pack/plugins/security_solution/public/common/components/toolbar/bulk_actions/alert_bulk_assignees.test.tsx b/x-pack/plugins/security_solution/public/common/components/toolbar/bulk_actions/alert_bulk_assignees.test.tsx
index a3a76c4bea327..2d7748cf76691 100644
--- a/x-pack/plugins/security_solution/public/common/components/toolbar/bulk_actions/alert_bulk_assignees.test.tsx
+++ b/x-pack/plugins/security_solution/public/common/components/toolbar/bulk_actions/alert_bulk_assignees.test.tsx
@@ -10,27 +10,57 @@ import type { UserProfileWithAvatar } from '@kbn/user-profile-components';
 import { act, fireEvent, render } from '@testing-library/react';
 import React from 'react';
 import { TestProviders } from '../../../mock';
+import { useGetUserProfiles } from '../../../../detections/containers/detection_engine/alerts/use_get_user_profiles';
 import { useSuggestUsers } from '../../../../detections/containers/detection_engine/alerts/use_suggest_users';
 
 import { BulkAlertAssigneesPanel } from './alert_bulk_assignees';
 import { ALERT_WORKFLOW_ASSIGNEE_IDS } from '@kbn/rule-data-utils';
 
+jest.mock('../../../../detections/containers/detection_engine/alerts/use_get_user_profiles');
 jest.mock('../../../../detections/containers/detection_engine/alerts/use_suggest_users');
 
 const mockUserProfiles: UserProfileWithAvatar[] = [
-  { uid: 'default-test-assignee-id-1', enabled: true, user: { username: 'user1' }, data: {} },
-  { uid: 'default-test-assignee-id-2', enabled: true, user: { username: 'user2' }, data: {} },
+  { uid: 'user-id-1', enabled: true, user: { username: 'user1' }, data: {} },
+  { uid: 'user-id-2', enabled: true, user: { username: 'user2' }, data: {} },
 ];
 
-const mockAssigneeItems = [
+const mockSuggestedUserProfiles: UserProfileWithAvatar[] = [
+  ...mockUserProfiles,
+  { uid: 'user-id-3', enabled: true, user: { username: 'user3' }, data: {} },
+  { uid: 'user-id-4', enabled: true, user: { username: 'user4' }, data: {} },
+];
+
+const mockAlertsWithAssignees = [
   {
     _id: 'test-id',
-    data: [{ field: ALERT_WORKFLOW_ASSIGNEE_IDS, value: ['assignee-id-1', 'assignee-id-2'] }],
+    data: [
+      {
+        field: ALERT_WORKFLOW_ASSIGNEE_IDS,
+        value: ['user-id-1', 'user-id-2'],
+      },
+    ],
+    ecs: { _id: 'test-id' },
+  },
+  {
+    _id: 'test-id',
+    data: [
+      {
+        field: ALERT_WORKFLOW_ASSIGNEE_IDS,
+        value: ['user-id-1', 'user-id-2'],
+      },
+    ],
     ecs: { _id: 'test-id' },
   },
 ];
 
-(useSuggestUsers as jest.Mock).mockReturnValue({ loading: false, userProfiles: mockUserProfiles });
+(useGetUserProfiles as jest.Mock).mockReturnValue({
+  loading: false,
+  userProfiles: mockUserProfiles,
+});
+(useSuggestUsers as jest.Mock).mockReturnValue({
+  loading: false,
+  userProfiles: mockSuggestedUserProfiles,
+});
 
 const renderAssigneesMenu = (
   items: TimelineItem[],
@@ -56,7 +86,7 @@ describe('BulkAlertAssigneesPanel', () => {
   });
 
   test('it renders', () => {
-    const wrapper = renderAssigneesMenu(mockAssigneeItems);
+    const wrapper = renderAssigneesMenu(mockAlertsWithAssignees);
 
     expect(wrapper.getByTestId('alert-assignees-update-button')).toBeInTheDocument();
     expect(useSuggestUsers).toHaveBeenCalled();
@@ -67,25 +97,8 @@ describe('BulkAlertAssigneesPanel', () => {
     const mockedOnSubmit = jest.fn();
     const mockedSetIsLoading = jest.fn();
 
-    const mockAssignees = [
-      {
-        _id: 'test-id',
-        data: [{ field: ALERT_WORKFLOW_ASSIGNEE_IDS, value: ['default-test-assignee-id-1'] }],
-        ecs: { _id: 'test-id' },
-      },
-      {
-        _id: 'test-id',
-        data: [
-          {
-            field: ALERT_WORKFLOW_ASSIGNEE_IDS,
-            value: ['default-test-assignee-id-1', 'default-test-assignee-id-2'],
-          },
-        ],
-        ecs: { _id: 'test-id' },
-      },
-    ];
     const wrapper = renderAssigneesMenu(
-      mockAssignees,
+      mockAlertsWithAssignees,
       mockedClosePopover,
       mockedOnSubmit,
       mockedSetIsLoading
@@ -100,40 +113,32 @@ describe('BulkAlertAssigneesPanel', () => {
   });
 
   test('it updates state correctly', () => {
-    const mockAssignees = [
-      {
-        _id: 'test-id',
-        data: [{ field: ALERT_WORKFLOW_ASSIGNEE_IDS, value: ['default-test-assignee-id-1'] }],
-        ecs: { _id: 'test-id' },
-      },
-      {
-        _id: 'test-id',
-        data: [
-          {
-            field: ALERT_WORKFLOW_ASSIGNEE_IDS,
-            value: ['default-test-assignee-id-1', 'default-test-assignee-id-2'],
-          },
-        ],
-        ecs: { _id: 'test-id' },
-      },
-    ];
-    const wrapper = renderAssigneesMenu(mockAssignees);
-
-    expect(wrapper.getAllByRole('option')[0]).toHaveAttribute('title', 'user1');
-    expect(wrapper.getAllByRole('option')[0]).toBeChecked();
-    act(() => {
-      fireEvent.click(wrapper.getByText('user1'));
-    });
-    expect(wrapper.getAllByRole('option')[0]).toHaveAttribute('title', 'user1');
-    expect(wrapper.getAllByRole('option')[0]).not.toBeChecked();
-
-    expect(wrapper.getAllByRole('option')[1]).toHaveAttribute('title', 'user2');
-    expect(wrapper.getAllByRole('option')[1]).not.toBeChecked();
-    act(() => {
-      fireEvent.click(wrapper.getByText('user2'));
-    });
-    expect(wrapper.getAllByRole('option')[1]).toHaveAttribute('title', 'user2');
-    expect(wrapper.getAllByRole('option')[1]).toBeChecked();
+    const wrapper = renderAssigneesMenu(mockAlertsWithAssignees);
+
+    const deselectUser = (userName: string, index: number) => {
+      expect(wrapper.getAllByRole('option')[index]).toHaveAttribute('title', userName);
+      expect(wrapper.getAllByRole('option')[index]).toBeChecked();
+      act(() => {
+        fireEvent.click(wrapper.getByText(userName));
+      });
+      expect(wrapper.getAllByRole('option')[index]).toHaveAttribute('title', userName);
+      expect(wrapper.getAllByRole('option')[index]).not.toBeChecked();
+    };
+
+    const selectUser = (userName: string, index = 0) => {
+      expect(wrapper.getAllByRole('option')[index]).toHaveAttribute('title', userName);
+      expect(wrapper.getAllByRole('option')[index]).not.toBeChecked();
+      act(() => {
+        fireEvent.click(wrapper.getByText(userName));
+      });
+      expect(wrapper.getAllByRole('option')[index]).toHaveAttribute('title', userName);
+      expect(wrapper.getAllByRole('option')[index]).toBeChecked();
+    };
+
+    deselectUser('user1', 0);
+    deselectUser('user2', 1);
+    selectUser('user3', 2);
+    selectUser('user4', 3);
   });
 
   test('it calls expected functions on submit when alerts have changed', () => {
@@ -141,25 +146,8 @@ describe('BulkAlertAssigneesPanel', () => {
     const mockedOnSubmit = jest.fn();
     const mockedSetIsLoading = jest.fn();
 
-    const mockAssignees = [
-      {
-        _id: 'test-id',
-        data: [{ field: ALERT_WORKFLOW_ASSIGNEE_IDS, value: ['default-test-assignee-id-1'] }],
-        ecs: { _id: 'test-id' },
-      },
-      {
-        _id: 'test-id',
-        data: [
-          {
-            field: ALERT_WORKFLOW_ASSIGNEE_IDS,
-            value: ['default-test-assignee-id-1', 'default-test-assignee-id-2'],
-          },
-        ],
-        ecs: { _id: 'test-id' },
-      },
-    ];
     const wrapper = renderAssigneesMenu(
-      mockAssignees,
+      mockAlertsWithAssignees,
       mockedClosePopover,
       mockedOnSubmit,
       mockedSetIsLoading
@@ -170,6 +158,12 @@ describe('BulkAlertAssigneesPanel', () => {
     act(() => {
       fireEvent.click(wrapper.getByText('user2'));
     });
+    act(() => {
+      fireEvent.click(wrapper.getByText('user3'));
+    });
+    act(() => {
+      fireEvent.click(wrapper.getByText('user4'));
+    });
 
     act(() => {
       fireEvent.click(wrapper.getByTestId('alert-assignees-update-button'));
@@ -178,8 +172,8 @@ describe('BulkAlertAssigneesPanel', () => {
     expect(mockedOnSubmit).toHaveBeenCalled();
     expect(mockedOnSubmit).toHaveBeenCalledWith(
       {
-        assignees_to_add: ['default-test-assignee-id-2'],
-        assignees_to_remove: ['default-test-assignee-id-1'],
+        assignees_to_add: ['user-id-4', 'user-id-3'],
+        assignees_to_remove: ['user-id-1', 'user-id-2'],
       },
       ['test-id', 'test-id'],
       expect.anything(), // An anonymous callback defined in the onSubmit function
diff --git a/x-pack/plugins/security_solution/public/common/components/toolbar/bulk_actions/use_bulk_alert_assignees_items.test.tsx b/x-pack/plugins/security_solution/public/common/components/toolbar/bulk_actions/use_bulk_alert_assignees_items.test.tsx
index 7a87744b49190..f04ae2aef3d2b 100644
--- a/x-pack/plugins/security_solution/public/common/components/toolbar/bulk_actions/use_bulk_alert_assignees_items.test.tsx
+++ b/x-pack/plugins/security_solution/public/common/components/toolbar/bulk_actions/use_bulk_alert_assignees_items.test.tsx
@@ -16,9 +16,11 @@ import type {
 } from './use_bulk_alert_assignees_items';
 import { useBulkAlertAssigneesItems } from './use_bulk_alert_assignees_items';
 import { useSetAlertAssignees } from './use_set_alert_assignees';
+import { useGetUserProfiles } from '../../../../detections/containers/detection_engine/alerts/use_get_user_profiles';
 import { useSuggestUsers } from '../../../../detections/containers/detection_engine/alerts/use_suggest_users';
 
 jest.mock('./use_set_alert_assignees');
+jest.mock('../../../../detections/containers/detection_engine/alerts/use_get_user_profiles');
 jest.mock('../../../../detections/containers/detection_engine/alerts/use_suggest_users');
 
 const mockUserProfiles: UserProfileWithAvatar[] = [
@@ -50,6 +52,10 @@ const renderPanel = (panel: UseBulkAlertAssigneesPanel) => {
 describe('useBulkAlertAssigneesItems', () => {
   beforeEach(() => {
     (useSetAlertAssignees as jest.Mock).mockReturnValue(jest.fn());
+    (useGetUserProfiles as jest.Mock).mockReturnValue({
+      loading: false,
+      userProfiles: mockUserProfiles,
+    });
     (useSuggestUsers as jest.Mock).mockReturnValue({
       loading: false,
       userProfiles: mockUserProfiles,
diff --git a/x-pack/plugins/security_solution/public/detections/components/alerts_table/timeline_actions/use_alert_assignees_actions.test.tsx b/x-pack/plugins/security_solution/public/detections/components/alerts_table/timeline_actions/use_alert_assignees_actions.test.tsx
index 5110f512a4610..a11441ed0f346 100644
--- a/x-pack/plugins/security_solution/public/detections/components/alerts_table/timeline_actions/use_alert_assignees_actions.test.tsx
+++ b/x-pack/plugins/security_solution/public/detections/components/alerts_table/timeline_actions/use_alert_assignees_actions.test.tsx
@@ -17,10 +17,12 @@ import React from 'react';
 import type { EuiContextMenuPanelDescriptor } from '@elastic/eui';
 import { EuiPopover, EuiContextMenu } from '@elastic/eui';
 import { useSetAlertAssignees } from '../../../../common/components/toolbar/bulk_actions/use_set_alert_assignees';
+import { useGetUserProfiles } from '../../../containers/detection_engine/alerts/use_get_user_profiles';
 import { useSuggestUsers } from '../../../containers/detection_engine/alerts/use_suggest_users';
 
 jest.mock('../../../containers/detection_engine/alerts/use_alerts_privileges');
 jest.mock('../../../../common/components/toolbar/bulk_actions/use_set_alert_assignees');
+jest.mock('../../../containers/detection_engine/alerts/use_get_user_profiles');
 jest.mock('../../../containers/detection_engine/alerts/use_suggest_users');
 
 const mockUserProfiles: UserProfileWithAvatar[] = [
@@ -160,6 +162,10 @@ describe('useAlertAssigneesActions', () => {
 
   it('should render the nested panel', async () => {
     (useSetAlertAssignees as jest.Mock).mockReturnValue(jest.fn());
+    (useGetUserProfiles as jest.Mock).mockReturnValue({
+      loading: false,
+      userProfiles: mockUserProfiles,
+    });
     (useSuggestUsers as jest.Mock).mockReturnValue({
       loading: false,
       userProfiles: mockUserProfiles,