Fix: escape Telegram MarkdownV2 after template rendering

server/notification-providers/telegram.js

@@ -1,9 +1,84 @@
 const NotificationProvider = require("./notification-provider");
 const axios = require("axios");
+const { Liquid } = require("liquidjs");
+const { DOWN } = require("../../src/util");
 
 class Telegram extends NotificationProvider {
     name = "telegram";
 
+    /**
+     * Escapes special characters for Telegram MarkdownV2 format
+     * @param {string} text Text to escape
+     * @returns {string} Escaped text
+     */
+    escapeMarkdownV2(text) {
+        if (!text) {
+            return text;
+        }
+
+        // Characters that need to be escaped in MarkdownV2
+        // https://core.telegram.org/bots/api#markdownv2-style
+        return String(text).replace(/[_*[\]()~>#+\-=|{}.!\\]/g, "\\$&");
+    }
+
+    /**
+     * Renders template with optional MarkdownV2 escaping
+     * @param {string} template The template
+     * @param {string} msg Base message
+     * @param {?object} monitorJSON Monitor details
+     * @param {?object} heartbeatJSON Heartbeat details
+     * @param {boolean} escapeMarkdown Whether to escape for MarkdownV2
+     * @returns {Promise<string>} Rendered template
+     */
+    async renderTemplate(template, msg, monitorJSON, heartbeatJSON, escapeMarkdown = false) {
+        const engine = new Liquid({
+            root: "./no-such-directory-uptime-kuma",
+            relativeReference: false,
+            dynamicPartials: false,
+        });
+
+        const parsedTpl = engine.parse(template);
+
+        // Defaults
+        let monitorName = "Monitor Name not available";
+        let monitorHostnameOrURL = "testing.hostname";
+
+        if (monitorJSON !== null) {
+            monitorName = monitorJSON.name;
+            monitorHostnameOrURL = this.extractAddress(monitorJSON);
+        }
+
+        let serviceStatus = "⚠️ Test";
+        if (heartbeatJSON !== null) {
+            serviceStatus = heartbeatJSON.status === DOWN ? "🔴 Down" : "✅ Up";
+        }
+
+        // Escape values only when MarkdownV2 is enabled
+        if (escapeMarkdown) {
+            msg = this.escapeMarkdownV2(msg);
+            monitorName = this.escapeMarkdownV2(monitorName);
+            monitorHostnameOrURL = this.escapeMarkdownV2(monitorHostnameOrURL);
+            serviceStatus = this.escapeMarkdownV2(serviceStatus);
+        }
+
+        const context = {
+            // v1 compatibility (remove in v3)
+            STATUS: serviceStatus,
+            NAME: monitorName,
+            HOSTNAME_OR_URL: monitorHostnameOrURL,
+
+            // Official variables
+            status: serviceStatus,
+            name: monitorName,
+            hostnameOrURL: monitorHostnameOrURL,
+            monitorJSON,
+            heartbeatJSON,
+            msg,
+        };
+
+        return engine.render(parsedTpl, context);
+    }
+
     /**
      * @inheritdoc
      */
@@ -24,7 +99,8 @@ class Telegram extends NotificationProvider {
             }
 
             if (notification.telegramUseTemplate) {
-                params.text = await this.renderTemplate(notification.telegramTemplate, msg, monitorJSON, heartbeatJSON);
+                const escapeMarkdown = notification.telegramTemplateParseMode === "MarkdownV2";
+                params.text = await this.renderTemplate(notification.telegramTemplate, msg, monitorJSON, heartbeatJSON, escapeMarkdown);
 
                 if (notification.telegramTemplateParseMode !== "plain") {
                     params.parse_mode = notification.telegramTemplateParseMode;