diff --git a/gotelegram-bot/bot.py b/gotelegram-bot/bot.py
index 408b64f..8c4ade7 100644
--- a/gotelegram-bot/bot.py
+++ b/gotelegram-bot/bot.py
@@ -240,6 +240,24 @@ async def sh(*args, timeout: int = 60) -> Tuple[int, str, str]:
         return (-1, "", str(e))
 
 
+# Per-host mutex preventing concurrent install.sh --action invocations. Two
+# admins hitting "change template" at the same second could race each other
+# and corrupt /var/www/gotelegram-site. One global lock is fine — these are
+# rare operations and should serialize cleanly.
+_BOT_ACTION_LOCK = asyncio.Lock()
+
+# Allowed template-id shape: catalog ids are [a-zA-Z0-9_-], never longer than 64.
+# This is a defense-in-depth check before we hand the value to subprocess.
+_TPL_ID_RE = re.compile(r"^[A-Za-z0-9_-]{1,64}$")
+
+# Allowed Lite mask domain shape — simple DNS hostname, up to 253 chars total.
+# Each label 1–63 chars, labels separated by dots, alphanumerics + hyphens.
+_DOMAIN_RE = re.compile(
+    r"^(?=.{1,253}$)(?:(?!-)[A-Za-z0-9-]{1,63}(?<!-)\.)+"
+    r"(?!-)[A-Za-z0-9-]{2,63}(?<!-)$"
+)
+
+
 async def run_bot_action(action: str, timeout: int = 300, **params) -> Dict:
     """Invoke install.sh --action=X --json and parse the JSON result.
 
@@ -324,12 +342,23 @@ def save_json(path: str, data: Dict) -> bool:
         return False
 
 
-async def safe_edit_message(query, text: str, reply_markup=None, parse_mode=None) -> bool:
-    """Safely edit message, handling cases where message was deleted or not modified."""
+async def safe_edit_message(
+    query,
+    text: str,
+    reply_markup=None,
+    parse_mode=None,
+    disable_web_page_preview: Optional[bool] = None,
+) -> bool:
+    """Safely edit message, handling cases where message was deleted or not modified.
+
+    `disable_web_page_preview` is forwarded to edit_message_text when set; omitting
+    it keeps Telegram's default (enabled).
+    """
+    kwargs = {"reply_markup": reply_markup, "parse_mode": parse_mode}
+    if disable_web_page_preview is not None:
+        kwargs["disable_web_page_preview"] = disable_web_page_preview
     try:
-        await query.edit_message_text(
-            text, reply_markup=reply_markup, parse_mode=parse_mode
-        )
+        await query.edit_message_text(text, **kwargs)
         return True
     except BadRequest as e:
         err_msg = str(e).lower()
@@ -621,11 +650,13 @@ async def get_status_text(user_id: Optional[int] = None) -> str:
     config = load_json(GOTELEGRAM_CONFIG)
     if config:
         lines.append(f"<b>{_t(user_id, 'status_mode')}:</b> {html.escape(str(config.get('mode', 'unknown')))}")
-        if "template" in config:
-            lines.append(f"<b>{_t(user_id, 'status_template')}:</b> {html.escape(str(config['template']))}")
-        if "domain" in config:
+        # install.sh/save_gotelegram_config uses "template_id" (not "template")
+        tpl = config.get("template_id") or config.get("template")
+        if tpl:
+            lines.append(f"<b>{_t(user_id, 'status_template')}:</b> {html.escape(str(tpl))}")
+        if config.get("domain"):
             lines.append(f"<b>{_t(user_id, 'status_domain')}:</b> {html.escape(str(config['domain']))}")
-        if "port" in config:
+        if config.get("port"):
             lines.append(f"<b>{_t(user_id, 'status_port')}:</b> {html.escape(str(config['port']))}")
 
     # Telemt config (v3: [server] port = ..., [censorship] tls_domain = ...)
@@ -878,6 +909,13 @@ async def cb_lite_domain(update: Update, context: ContextTypes.DEFAULT_TYPE) ->
         await query.answer("Invalid domain selection")
         return
 
+    # Defense-in-depth: LITE_DOMAINS is trusted, but validate the shape anyway
+    # in case someone extends the list with garbage later.
+    if not _DOMAIN_RE.match(domain):
+        logger.warning(f"cb_lite_domain: rejecting malformed domain {domain!r}")
+        await query.answer("Invalid domain")
+        return
+
     await query.answer()
 
     config = load_json(GOTELEGRAM_CONFIG) or {}
@@ -898,6 +936,18 @@ async def cb_lite_domain(update: Update, context: ContextTypes.DEFAULT_TYPE) ->
         return
 
     # Lite active — switch fake-TLS mask domain in place
+    if _BOT_ACTION_LOCK.locked():
+        await safe_edit_message(
+            query,
+            "<b>⏳ Другая операция уже выполняется</b>\n\n"
+            "Дождитесь завершения предыдущей смены шаблона/домена и повторите.",
+            reply_markup=InlineKeyboardMarkup(
+                [[InlineKeyboardButton(_t(_uid(update), "btn_back"), callback_data="menu_main")]]
+            ),
+            parse_mode="HTML",
+        )
+        return
+
     progress_text = (
         "<b>⏳ Меняю маскировочный домен...</b>\n\n"
         f"Новый домен: <code>{html.escape(domain)}</code>\n\n"
@@ -905,7 +955,8 @@ async def cb_lite_domain(update: Update, context: ContextTypes.DEFAULT_TYPE) ->
     )
     await safe_edit_message(query, progress_text, parse_mode="HTML")
 
-    result = await run_bot_action("change-lite-domain", timeout=30, domain=domain)
+    async with _BOT_ACTION_LOCK:
+        result = await run_bot_action("change-lite-domain", timeout=30, domain=domain)
 
     if result.get("status") == "success":
         text = (
@@ -1219,6 +1270,21 @@ async def cb_pro_confirm(update: Update, context: ContextTypes.DEFAULT_TYPE) ->
 
     await query.answer()
 
+    # Defense-in-depth: even though subprocess.exec uses list args (no shell),
+    # we still enforce the catalog id shape before handing it to install.sh.
+    if not _TPL_ID_RE.match(tpl_id):
+        logger.warning(f"cb_pro_confirm: rejecting malformed tpl_id {tpl_id!r}")
+        await safe_edit_message(
+            query,
+            "<b>❌ Некорректный идентификатор шаблона</b>\n\n"
+            "Выбран неподдерживаемый шаблон. Вернитесь в меню и попробуйте снова.",
+            reply_markup=InlineKeyboardMarkup(
+                [[InlineKeyboardButton(_t(_uid(update), "btn_back"), callback_data="menu_main")]]
+            ),
+            parse_mode="HTML",
+        )
+        return
+
     # Read current config to decide: in-place change-template vs fresh install
     config = load_json(GOTELEGRAM_CONFIG) or {}
     current_mode = config.get("mode", "")
@@ -1240,6 +1306,18 @@ async def cb_pro_confirm(update: Update, context: ContextTypes.DEFAULT_TYPE) ->
         return
 
     # Pro mode is active — perform change-template in place
+    if _BOT_ACTION_LOCK.locked():
+        await safe_edit_message(
+            query,
+            "<b>⏳ Другая операция уже выполняется</b>\n\n"
+            "Дождитесь завершения предыдущей смены шаблона/домена и повторите.",
+            reply_markup=InlineKeyboardMarkup(
+                [[InlineKeyboardButton(_t(_uid(update), "btn_back"), callback_data="menu_main")]]
+            ),
+            parse_mode="HTML",
+        )
+        return
+
     progress_text = (
         "<b>⏳ Меняю шаблон сайта...</b>\n\n"
         f"Шаблон: <code>{html.escape(tpl_id)}</code>\n\n"
@@ -1248,8 +1326,10 @@ async def cb_pro_confirm(update: Update, context: ContextTypes.DEFAULT_TYPE) ->
     )
     await safe_edit_message(query, progress_text, parse_mode="HTML")
 
-    # Template download + git clone can be slow — generous timeout
-    result = await run_bot_action("change-template", timeout=180, template=tpl_id)
+    # Template download + git clone can be slow — generous timeout.
+    # Mutex serializes with any concurrent change-lite-domain/change-template.
+    async with _BOT_ACTION_LOCK:
+        result = await run_bot_action("change-template", timeout=180, template=tpl_id)
 
     if result.get("status") == "success":
         domain = result.get("domain", config.get("domain", ""))
@@ -2209,9 +2289,10 @@ async def handle_text_message(update: Update, context: ContextTypes.DEFAULT_TYPE
     if not ok:
         await update.message.reply_text(_t(user_id, info), parse_mode="HTML")
         return
-    # Success — record in GoTelegram config
+    # Success — record in GoTelegram config. Use "template_id" (canonical
+    # field name written by install.sh/save_gotelegram_config).
     config = load_json(GOTELEGRAM_CONFIG) or {}
-    config["template"] = tpl_id
+    config["template_id"] = tpl_id
     config["template_source"] = url
     save_json(GOTELEGRAM_CONFIG, config)
     await update.message.reply_text(
diff --git a/install.sh b/install.sh
index a9c5d10..fa1c0cf 100755
--- a/install.sh
+++ b/install.sh
@@ -1168,17 +1168,20 @@ bot_emit_json() {
     printf '{"status":"%s","message":"%s"%s}\n' "$status" "$msg_esc" "$extra"
 }
 
-# Update a single key in config.json without rewriting the whole file
+# Update a single key in config.json without rewriting the whole file.
+# Uses `date -Iseconds` rather than jq's `now | todate` — the latter requires
+# jq 1.6+ which is not available on Debian 10 or older CentOS.
 bot_update_config_field() {
     local key="$1"
     local value="$2"
     if [ ! -f "$GOTELEGRAM_CONFIG" ]; then
         return 1
     fi
-    local tmp
+    local tmp now
     tmp=$(mktemp) || return 1
-    if jq --arg k "$key" --arg v "$value" \
-        '.[$k] = $v | .updated_at = (now | todate)' \
+    now=$(date -Iseconds 2>/dev/null || date +%Y-%m-%dT%H:%M:%S%z)
+    if jq --arg k "$key" --arg v "$value" --arg t "$now" \
+        '.[$k] = $v | .updated_at = $t' \
         "$GOTELEGRAM_CONFIG" > "$tmp" 2>/dev/null; then
         mv "$tmp" "$GOTELEGRAM_CONFIG"
         chmod 600 "$GOTELEGRAM_CONFIG"