diff --git a/class/GroupMgr.php b/class/GroupMgr.php
index c1b5c75..36cd02d 100644
--- a/class/GroupMgr.php
+++ b/class/GroupMgr.php
@@ -42,7 +42,8 @@ class Group extends AutoStoring
     // Create Group from array
     static function fromArray(GroupMgr &$groupMgr, array $a): Group
     {
-        return new Group($groupMgr, $a["groupname"], $a["description"], $a["owner"], $a["_id"], $a["unique"], $a["editors"], $a["users"], $a["games"]);
+        $id = $a["_id"] ?? -1;
+        return new Group($groupMgr, $a["groupname"], $a["description"], $a["owner"], $id, $a["unique"], $a["editors"], $a["users"], $a["games"]);
     }
 
     // Convert Group to array
@@ -170,6 +171,16 @@ class Group extends AutoStoring
         $this->storeMods(); // store changes
     }
 
+    // Add members
+    function addMembers(array $nicknames) : void {
+        $this->changeMembers($nicknames, []);
+    }
+
+    // Remove members
+    function removeMembers(array $nicknames) : void {
+        $this->changeMembers([], $nicknames);
+    }
+
     // Include/exclude games.
     function changeGames(array $gameids_add, array $gameids_remove): void
     {
@@ -266,7 +277,7 @@ class GroupMgr
             "owner" => $owner,
             "description" => $description,
             "editors" => [],
-            "members" => [],
+            "users" => [],
             "games" => []
         ];
 
diff --git a/class/UserMgr.php b/class/UserMgr.php
index 2886b38..402faf8 100644
--- a/class/UserMgr.php
+++ b/class/UserMgr.php
@@ -221,4 +221,10 @@ class UserMgr
         $qb = $this->db->createQueryBuilder();
         return array_map(fn($c): string => $c["nickname"], $qb->select(["nickname"])->getQuery()->fetch());
     }
+
+    // Sanitize nicknames. Clear non-existent nicknames from the array.
+    function sanitizeNicknames(array $nicknames): array {
+        $a = $this->db->findBy(["nickname", "IN", $nicknames]);
+        return array_map(fn($a) => $a["nickname"], $a);
+    }
 }
\ No newline at end of file
diff --git a/common_func.php b/common_func.php
index 0523946..5c5a463 100644
--- a/common_func.php
+++ b/common_func.php
@@ -1,7 +1,11 @@
 <?php
 
 function explode_list(string $str) : array {
-    return explode(",", str_replace(" ", "", $str));
+    if (trim($str) !== "") {
+        return explode(",", str_replace(" ", "", $str));
+    } else {
+        return [];
+    }
 }
 
 function alter_array_contents(array &$a, $add, $remove) {
diff --git a/group_manager_frame.php b/group_manager_frame.php
index 9a95a1f..b90c5f4 100644
--- a/group_manager_frame.php
+++ b/group_manager_frame.php
@@ -63,8 +63,14 @@ if (!get_autologin_state() || ($user_data["privilege"] !== PRIVILEGE_QUIZMASTER)
                 <td><input type="text" id="group_editors"></td>
             </tr>
             <tr>
-                <td><label for="group_members">Tagok:</label></td>
-                <td><textarea id="group_members" readonly></textarea></td>
+                <td>
+                    <label for="group_members">Tagok:</label><br>
+                    <input type="button" value="+" onclick="open_member_change_window('add')">
+                    <input type="button" value="-" onclick="open_member_change_window('remove')">
+                </td>
+                <td>
+                    <textarea id="group_members" readonly></textarea>
+                </td>
             </tr>
         </table>
         <section style="display: block; text-align: right">
@@ -74,6 +80,16 @@ if (!get_autologin_state() || ($user_data["privilege"] !== PRIVILEGE_QUIZMASTER)
     </section>
 </section>
 
+<section class="window" shown="false" id="member_manager_window">
+    <section class="window-inner">
+        <section id="member_manager_window_title">
+        </section>
+        <textarea id="add_remove_member_area"></textarea><br>
+        <input type="button" value="OK" onclick="change_group_members()">
+        <input type="button" value="Mégse" onclick="hide('member_manager_window')">
+    </section>
+</section>
+
 <script>
     list_all_groups();
 </script>
diff --git a/interface.php b/interface.php
index acc2031..e9c04da 100644
--- a/interface.php
+++ b/interface.php
@@ -322,10 +322,8 @@ $requester_nickname = $is_quizmaster ? "*" : $nickname; // "*" means every game
 
 function create_update_game(ReqHandler &$rh, array $params): array
 {
-    global $userMgr;
     global $user;
     global $nickname;
-    global $is_quizmaster;
     global $gameMgr;
 
     $update = $params[ReqHandler::ACTION_KEY] === "update_game";
@@ -340,20 +338,8 @@ function create_update_game(ReqHandler &$rh, array $params): array
     $description = $data["description"];
     $contributors = explode_list($data["contributors"] ?? "");
     $owner = $update ? trim($data["owner"] ?? $nickname) : $nickname;
-    $groups = explode_list($data["groups"] ?? "");
     $properties = $data["properties"] ?? [];
 
-    // convert group compounds to group IDs
-    $groupids = get_groupids_by_compounds($groups); // convert group compounds to _ids
-
-    // remove group ID's this user cannot edit
-//    $groupids_with_editor_access = [];
-//    foreach ($groupids as $groupid) {
-//        if (is_user_editor_to_group($groupid, $nickname) || $is_quizmaster) {
-//            $groupids_with_editor_access[] = $groupid;
-//        }
-//    }
-
     // result
     $result = [];
 
@@ -364,21 +350,6 @@ function create_update_game(ReqHandler &$rh, array $params): array
         $game = $gameMgr->getGame($gameid); // fetch game
 
         if (($game !== null) && $game->isUserContributorOrOwner($nickname) || $user->hasQuizmasterPrivilege()) {
-            // group management TODO: átkerül a csoportkezelőbe
-//            $old_groupids = $game_data["groups"]; // retain old groupids
-//            $new_groupids = $groupids; // get new groupids
-//            $groupids_add = array_diff($new_groupids, $old_groupids); // groups this user needs to be added to
-//            $groupids_remove = array_diff($old_groupids, $new_groupids); // groups this user need to be removed from
-//            foreach ($groupids_add as $groupid) { // execute insertion and removal
-//                change_group_game_assignments($groupid, $gameid, null);
-//            }
-//            foreach ($groupids_remove as $groupid) {
-//                change_group_game_assignments($groupid, null, $gameid);
-//            }
-
-            // re-fetch game data
-//            $game_data = get_game($gameid);
-
             // disable autostoring
             $game->disableAutoStoring();
 
@@ -644,31 +615,13 @@ function create_update_user(ReqHandler &$rh, array $params): string
     $realname = trim($params["realname"]);
     $privilege = trim($params["privilege"]);
 
-    // $groupids = get_groupids_by_compounds($groups); // convert group compounds to _ids FIXME!!!
-
     $success = false;
     if (($target_nickname !== "")) {
         if ((!$update) && ($password !== "")) { // CREATE
-            $success = $userMgr->addUser($target_nickname, $password, $realname, $privilege); // FIXME!!!
+            $success = $userMgr->addUser($target_nickname, $password, $realname, $privilege);
         } else if ($update) { // UPDATE
             $tuser = $userMgr->getUser($target_nickname); // load user data
             if ($tuser !== null) {
-
-                // group management FIXME!!!
-//                $old_groupids = $tuser->getGroups(); // retain old groupids
-//                $new_groupids = $groupids; // get new groupids
-//                $groupids_add = array_diff($new_groupids, $old_groupids); // groups this user needs to be added to
-//                $groupids_remove = array_diff($old_groupids, $new_groupids); // groups this user need to be removed from
-//                foreach ($groupids_add as $groupid) { // execute insertion and removal
-//                    change_group_user_assignments($groupid, $target_nickname, null);
-//                }
-//                foreach ($groupids_remove as $groupid) {
-//                    change_group_user_assignments($groupid, null, $target_nickname);
-//                }
-
-                // re-fetch user
-                //$tuser = get_user($target_nickname); // load user data
-
                 // further field update
                 $tuser->disableAutoStoring();
                 $tuser->setRealname($realname);
@@ -727,6 +680,26 @@ function get_game_groups(ReqHandler &$rh, array $params): array {
     return $groups;
 }
 
+function change_group_members(ReqHandler &$rh, array $params): string {
+    global $groupMgr;
+    global $user;
+    global $userMgr;
+
+    $group = $groupMgr->getGroup($params["groupid"]);
+    if ($group !== null) {
+        if ($group->isUserContributor($user->getNickname())) {
+            $add = explode_list(trim($params["add"]));
+            $add = $userMgr->sanitizeNicknames($add);
+            $remove = explode_list(trim($params["remove"]));
+            $remove = $userMgr->sanitizeNicknames($remove);
+            $group->changeMembers($add, $remove);
+            return "OK";
+        }
+    }
+
+    return "FAIL";
+}
+
 function import_users_from_csv(ReqHandler &$rh, array $params): string
 {
     if (!isset($_FILES["users_table"])) {
@@ -740,6 +713,7 @@ $rh->add("update_group", ["groupname", "description", "owner", "editors", "id"],
 $rh->add("delete_groups", ["ids"], PRIVILEGE_QUIZMASTER, "delete_groups", RESP_PLAIN, "Delete group.");
 $rh->add("get_all_groups", [], PRIVILEGE_QUIZMASTER, "get_all_player_groups", RESP_JSON, "Get all player groups.");
 $rh->add("search_groups", ["needle"], PRIVILEGE_QUIZMASTER, "search_player_groups", RESP_JSON, "Serach and fetch player groups.");
+$rh->add("change_group_members", ["groupid", "add", "remove"], PRIVILEGE_QUIZMASTER,"change_group_members", RESP_PLAIN, "Change group members.");
 
 $rh->add(["create_user", "update_user"], ["nickname", "password", "realname", "privilege"], PRIVILEGE_QUIZMASTER, "create_update_user", RESP_PLAIN, "Create or update user.");
 $rh->add("delete_users", ["users"], PRIVILEGE_QUIZMASTER, "delete_users", RESP_PLAIN, "Delete users.");
diff --git a/js/groupmgr.js b/js/groupmgr.js
index c489886..172de25 100644
--- a/js/groupmgr.js
+++ b/js/groupmgr.js
@@ -31,9 +31,13 @@ function list_all_groups() {
     });
 }
 
+let EDITED_GROUP = null;
+
 function create_edit_group(group = null) {
     let update = group !== null;
 
+    EDITED_GROUP = group;
+
     let groupnameF = document.getElementById("groupname");
     let group_descriptionF = document.getElementById("group_description");
     let submit_btn = document.getElementById("group_editor_submit_btn");
@@ -122,4 +126,42 @@ function print_group_name(group_data) {
         record += "#" + group_data["_id"];
     }
     return record;
+}
+
+let MEMBER_ACTION = "";
+
+function open_member_change_window(action) {
+    MEMBER_ACTION = action;
+    let winCap = document.getElementById("member_manager_window_title");
+
+    // print window title
+    if (action === "add") {
+        winCap.innerText = "Tagok hozzáadása";
+    } else if (action === "remove") {
+        winCap.innerText = "Tagok eltávolítása";
+    }
+
+    show("member_manager_window");
+}
+
+function change_group_members() {
+    let userListTA = document.getElementById("add_remove_member_area");
+
+    let req = {
+        action: "change_group_members",
+        groupid: EDITED_GROUP["_id"],
+        add: [],
+        remove: []
+    };
+
+    if (MEMBER_ACTION === "add") {
+        req["add"] = userListTA.value;
+    } else if (MEMBER_ACTION === "remove") {
+        req["remove"] = userListTA.value;
+    }
+
+    request(req).then(resp => {
+        userListTA.value = "";
+        hide("member_manager_window");
+    });
 }
\ No newline at end of file
diff --git a/js/result_analyzer.js b/js/result_analyzer.js
index b526cab..fec5b8c 100644
--- a/js/result_analyzer.js
+++ b/js/result_analyzer.js
@@ -204,11 +204,13 @@ function toggle_test_selection() {
 }
 
 function delete_tests() {
-    let req = {
-        action: "delete_tests",
-        ids: get_selected_ids().join(",")
-    };
-    request(req).then(resp => {
-       fetch_results(); // refresh results
-    });
+    if (confirm("Biztosan törölni kívánja a kijelölt eredményeket?")) {
+        let req = {
+            action: "delete_tests",
+            ids: get_selected_ids().join(",")
+        };
+        request(req).then(resp => {
+            fetch_results(); // refresh results
+        });
+    }
 }
\ No newline at end of file