diff --git a/x-pack/plugins/cases/public/components/case_view/components/case_view_activity.tsx b/x-pack/plugins/cases/public/components/case_view/components/case_view_activity.tsx
index 86a4ce588300c..ead3bc72645dd 100644
--- a/x-pack/plugins/cases/public/components/case_view/components/case_view_activity.tsx
+++ b/x-pack/plugins/cases/public/components/case_view/components/case_view_activity.tsx
@@ -242,7 +242,7 @@ export const CaseViewActivity = ({
             users={reporterAsArray}
             userProfiles={userProfiles}
           />
-          {caseUsers?.participants ? (
+          {caseUsers != null ? (
             <UserList
               dataTestSubj="case-view-user-list-participants"
               theCase={caseData}
diff --git a/x-pack/test/cases_api_integration/common/lib/api/user_profiles.ts b/x-pack/test/cases_api_integration/common/lib/api/user_profiles.ts
index 7cf75968d865b..add8093e93c23 100644
--- a/x-pack/test/cases_api_integration/common/lib/api/user_profiles.ts
+++ b/x-pack/test/cases_api_integration/common/lib/api/user_profiles.ts
@@ -12,6 +12,7 @@ import { UserProfileBulkGetParams, UserProfileServiceStart } from '@kbn/security
 import { INTERNAL_SUGGEST_USER_PROFILES_URL } from '@kbn/cases-plugin/common/constants';
 import { SuggestUserProfilesRequest } from '@kbn/cases-plugin/common/api';
 import { UserProfileService } from '@kbn/cases-plugin/server/services';
+import { UserProfileAvatarData } from '@kbn/security-plugin/common';
 import { superUser } from '../authentication/users';
 import { User } from '../authentication/types';
 import { getSpaceUrlPrefix } from './helpers';
@@ -70,6 +71,31 @@ export const suggestUserProfiles = async ({
   return profiles;
 };
 
+/**
+ * Updates the avatar of a user.
+ * The API needs a valid user session.
+ * The session acts as the user identifier
+ * whose the avatar is updated.
+ */
+export const updateUserProfileAvatar = async ({
+  supertest,
+  req,
+  expectedHttpCode = 200,
+  headers = {},
+}: {
+  supertest: SuperTest.SuperTest<SuperTest.Test>;
+  req: UserProfileAvatarData;
+  expectedHttpCode?: number;
+  headers?: Record<string, unknown>;
+}): Promise<void> => {
+  await supertest
+    .post('/internal/security/user_profile/_data')
+    .set('kbn-xsrf', 'true')
+    .set(headers)
+    .send({ avatar: req })
+    .expect(expectedHttpCode);
+};
+
 export const loginUsers = async ({
   supertest,
   users = [superUser],
diff --git a/x-pack/test/cases_api_integration/security_and_spaces/tests/common/internal/user_actions_get_users.ts b/x-pack/test/cases_api_integration/security_and_spaces/tests/common/internal/user_actions_get_users.ts
index 0f9fb10a9becb..e72a109eceeed 100644
--- a/x-pack/test/cases_api_integration/security_and_spaces/tests/common/internal/user_actions_get_users.ts
+++ b/x-pack/test/cases_api_integration/security_and_spaces/tests/common/internal/user_actions_get_users.ts
@@ -8,6 +8,7 @@
 import expect from '@kbn/expect';
 import { Cookie } from 'tough-cookie';
 import { UserProfile } from '@kbn/security-plugin/common';
+import { GetCaseUsersResponseRt } from '@kbn/cases-plugin/common/api';
 import { securitySolutionOnlyAllSpacesRole } from '../../../../common/lib/authentication/roles';
 import { getPostCaseRequest } from '../../../../common/lib/mock';
 import {
@@ -18,6 +19,7 @@ import {
   getCaseUsers,
   loginUsers,
   bulkGetUserProfiles,
+  updateUserProfileAvatar,
 } from '../../../../common/lib/api';
 import { FtrProviderContext } from '../../../../common/ftr_provider_context';
 import { createUsersAndRoles, deleteUsersAndRoles } from '../../../../common/lib/authentication';
@@ -167,204 +169,256 @@ export default ({ getService }: FtrProviderContext): void => {
         );
       });
 
-      it('returns only the creator of the case', async () => {
-        const postedCase = await createCase(
-          supertestWithoutAuth,
-          getPostCaseRequest(),
-          200,
-          null,
-          superUserHeaders
-        );
+      describe('schema', () => {
+        it('ensures that the schema of security plugin is as expected', async () => {
+          const avatar = {
+            initials: 'ES',
+            color: '#6092C0',
+            imageUrl: 'my-image',
+          };
+
+          // update user profile avatar
+          await updateUserProfileAvatar({
+            supertest,
+            req: avatar,
+            headers: superUserHeaders,
+          });
 
-        const { participants, assignees, unassignedUsers, reporter } = await getCaseUsers({
-          caseId: postedCase.id,
-          supertest,
+          const res = await bulkGetUserProfiles({
+            supertest: supertestWithoutAuth,
+            req: {
+              uids: [superUserProfile.uid],
+              dataPath: 'avatar',
+            },
+          });
+
+          const userProfile = res[0];
+
+          try {
+            const userToValidate = {
+              user: {
+                email: userProfile.user.email ?? null,
+                full_name: userProfile.user.full_name ?? null,
+                username: userProfile.user.username ?? null,
+              },
+              avatar,
+              uid: userProfile.uid,
+            };
+
+            GetCaseUsersResponseRt.encode({
+              assignees: [userToValidate],
+              unassignedUsers: [userToValidate],
+              participants: [userToValidate],
+              reporter: userToValidate,
+            });
+          } catch (error) {
+            throw new Error(
+              `Failed encoding GetCaseUsersResponse schema. Schema mismatch between Case users and Security user profiles. Error message: ${error}`
+            );
+          }
         });
+      });
 
-        expect(participants).to.eql([
-          {
+      describe('case users', () => {
+        it('returns only the creator of the case', async () => {
+          const postedCase = await createCase(
+            supertestWithoutAuth,
+            getPostCaseRequest(),
+            200,
+            null,
+            superUserHeaders
+          );
+
+          const { participants, assignees, unassignedUsers, reporter } = await getCaseUsers({
+            caseId: postedCase.id,
+            supertest,
+          });
+
+          expect(participants).to.eql([
+            {
+              user: {
+                username: superUserProfile.user.username,
+                full_name: superUserProfile.user.full_name,
+                email: superUserProfile.user.email,
+              },
+              uid: superUserProfile.uid,
+            },
+          ]);
+
+          expect(reporter).to.eql({
             user: {
               username: superUserProfile.user.username,
               full_name: superUserProfile.user.full_name,
               email: superUserProfile.user.email,
             },
             uid: superUserProfile.uid,
-          },
-        ]);
+          });
 
-        expect(reporter).to.eql({
-          user: {
-            username: superUserProfile.user.username,
-            full_name: superUserProfile.user.full_name,
-            email: superUserProfile.user.email,
-          },
-          uid: superUserProfile.uid,
+          expect(assignees).to.eql([]);
+          expect(unassignedUsers).to.eql([]);
         });
 
-        expect(assignees).to.eql([]);
-        expect(unassignedUsers).to.eql([]);
-      });
-
-      it('returns one participant if it is the only one that participates to the case', async () => {
-        const postedCase = await createCase(
-          supertestWithoutAuth,
-          getPostCaseRequest(),
-          200,
-          null,
-          superUserHeaders
-        );
+        it('returns one participant if it is the only one that participates to the case', async () => {
+          const postedCase = await createCase(
+            supertestWithoutAuth,
+            getPostCaseRequest(),
+            200,
+            null,
+            superUserHeaders
+          );
+
+          await changeCaseTitle({
+            supertest,
+            caseId: postedCase.id,
+            version: postedCase.version,
+            title: 'new title',
+            headers: superUserHeaders,
+          });
 
-        await changeCaseTitle({
-          supertest,
-          caseId: postedCase.id,
-          version: postedCase.version,
-          title: 'new title',
-          headers: superUserHeaders,
-        });
+          const { participants, assignees, unassignedUsers, reporter } = await getCaseUsers({
+            caseId: postedCase.id,
+            supertest,
+          });
 
-        const { participants, assignees, unassignedUsers, reporter } = await getCaseUsers({
-          caseId: postedCase.id,
-          supertest,
-        });
+          expect(participants).to.eql([
+            {
+              user: {
+                username: superUserProfile.user.username,
+                full_name: superUserProfile.user.full_name,
+                email: superUserProfile.user.email,
+              },
+              uid: superUserProfile.uid,
+            },
+          ]);
 
-        expect(participants).to.eql([
-          {
+          expect(reporter).to.eql({
             user: {
               username: superUserProfile.user.username,
               full_name: superUserProfile.user.full_name,
               email: superUserProfile.user.email,
             },
             uid: superUserProfile.uid,
-          },
-        ]);
+          });
 
-        expect(reporter).to.eql({
-          user: {
-            username: superUserProfile.user.username,
-            full_name: superUserProfile.user.full_name,
-            email: superUserProfile.user.email,
-          },
-          uid: superUserProfile.uid,
+          expect(assignees).to.eql([]);
+          expect(unassignedUsers).to.eql([]);
         });
 
-        expect(assignees).to.eql([]);
-        expect(unassignedUsers).to.eql([]);
-      });
-
-      it('returns all participants of the case', async () => {
-        const postedCase = await createCase(
-          supertestWithoutAuth,
-          getPostCaseRequest(),
-          200,
-          null,
-          superUserHeaders
-        );
-
-        await changeCaseTitle({
-          supertest,
-          caseId: postedCase.id,
-          version: postedCase.version,
-          title: 'new title',
-          headers: secOnlyHeaders,
-        });
+        it('returns all participants of the case', async () => {
+          const postedCase = await createCase(
+            supertestWithoutAuth,
+            getPostCaseRequest(),
+            200,
+            null,
+            superUserHeaders
+          );
+
+          await changeCaseTitle({
+            supertest,
+            caseId: postedCase.id,
+            version: postedCase.version,
+            title: 'new title',
+            headers: secOnlyHeaders,
+          });
 
-        const { participants, assignees, unassignedUsers, reporter } = await getCaseUsers({
-          caseId: postedCase.id,
-          supertest,
-        });
+          const { participants, assignees, unassignedUsers, reporter } = await getCaseUsers({
+            caseId: postedCase.id,
+            supertest,
+          });
 
-        expect(participants).to.eql([
-          {
-            user: {
-              username: secUserProfile.user.username,
-              full_name: secUserProfile.user.full_name,
-              email: secUserProfile.user.email,
+          expect(participants).to.eql([
+            {
+              user: {
+                username: secUserProfile.user.username,
+                full_name: secUserProfile.user.full_name,
+                email: secUserProfile.user.email,
+              },
+              uid: secUserProfile.uid,
             },
-            uid: secUserProfile.uid,
-          },
-          {
+            {
+              user: {
+                username: superUserProfile.user.username,
+                full_name: superUserProfile.user.full_name,
+                email: superUserProfile.user.email,
+              },
+              uid: superUserProfile.uid,
+            },
+          ]);
+
+          expect(reporter).to.eql({
             user: {
               username: superUserProfile.user.username,
               full_name: superUserProfile.user.full_name,
               email: superUserProfile.user.email,
             },
             uid: superUserProfile.uid,
-          },
-        ]);
+          });
 
-        expect(reporter).to.eql({
-          user: {
-            username: superUserProfile.user.username,
-            full_name: superUserProfile.user.full_name,
-            email: superUserProfile.user.email,
-          },
-          uid: superUserProfile.uid,
+          expect(assignees).to.eql([]);
+          expect(unassignedUsers).to.eql([]);
         });
 
-        expect(assignees).to.eql([]);
-        expect(unassignedUsers).to.eql([]);
-      });
-
-      it('does not return duplicate participants', async () => {
-        const postedCase = await createCase(
-          supertestWithoutAuth,
-          getPostCaseRequest(),
-          200,
-          null,
-          superUserHeaders
-        );
-
-        const updatedCases = await changeCaseTitle({
-          supertest,
-          caseId: postedCase.id,
-          version: postedCase.version,
-          title: 'new title',
-          headers: secOnlyHeaders,
-        });
+        it('does not return duplicate participants', async () => {
+          const postedCase = await createCase(
+            supertestWithoutAuth,
+            getPostCaseRequest(),
+            200,
+            null,
+            superUserHeaders
+          );
+
+          const updatedCases = await changeCaseTitle({
+            supertest,
+            caseId: postedCase.id,
+            version: postedCase.version,
+            title: 'new title',
+            headers: secOnlyHeaders,
+          });
 
-        await changeCaseDescription({
-          supertest,
-          caseId: updatedCases[0].id,
-          version: updatedCases[0].version,
-          description: 'new desc',
-          headers: secOnlyHeaders,
-        });
+          await changeCaseDescription({
+            supertest,
+            caseId: updatedCases[0].id,
+            version: updatedCases[0].version,
+            description: 'new desc',
+            headers: secOnlyHeaders,
+          });
 
-        const { participants, assignees, unassignedUsers, reporter } = await getCaseUsers({
-          caseId: postedCase.id,
-          supertest,
-        });
+          const { participants, assignees, unassignedUsers, reporter } = await getCaseUsers({
+            caseId: postedCase.id,
+            supertest,
+          });
 
-        expect(participants).to.eql([
-          {
-            user: {
-              username: secUserProfile.user.username,
-              full_name: secUserProfile.user.full_name,
-              email: secUserProfile.user.email,
+          expect(participants).to.eql([
+            {
+              user: {
+                username: secUserProfile.user.username,
+                full_name: secUserProfile.user.full_name,
+                email: secUserProfile.user.email,
+              },
+              uid: secUserProfile.uid,
             },
-            uid: secUserProfile.uid,
-          },
-          {
+            {
+              user: {
+                username: superUserProfile.user.username,
+                full_name: superUserProfile.user.full_name,
+                email: superUserProfile.user.email,
+              },
+              uid: superUserProfile.uid,
+            },
+          ]);
+
+          expect(reporter).to.eql({
             user: {
               username: superUserProfile.user.username,
               full_name: superUserProfile.user.full_name,
               email: superUserProfile.user.email,
             },
             uid: superUserProfile.uid,
-          },
-        ]);
+          });
 
-        expect(reporter).to.eql({
-          user: {
-            username: superUserProfile.user.username,
-            full_name: superUserProfile.user.full_name,
-            email: superUserProfile.user.email,
-          },
-          uid: superUserProfile.uid,
+          expect(assignees).to.eql([]);
+          expect(unassignedUsers).to.eql([]);
         });
-
-        expect(assignees).to.eql([]);
-        expect(unassignedUsers).to.eql([]);
       });
     });