fix: escape Telegram MarkdownV2 after template rendering (#6579)

Author: CommanderStorm

server/notification-providers/telegram.js

@@ -4,6 +4,47 @@ const axios = require("axios");
 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, "\\$&");
+    }
+
+    /**
+     * Recursively escapes string properties of an object for Telegram MarkdownV2
+     * @param {object|string} obj Object or string to escape
+     * @returns {object|string} Escaped object or string
+     */
+    escapeObjectRecursive(obj) {
+        if (typeof obj === "string") {
+            return this.escapeMarkdownV2(obj);
+        }
+        if (typeof obj === "object" && obj !== null) {
+            // Check if array
+            if (Array.isArray(obj)) {
+                return obj.map(item => this.escapeObjectRecursive(item));
+            }
+
+            const newObj = {};
+            for (const key in obj) {
+                if (Object.prototype.hasOwnProperty.call(obj, key)) {
+                    newObj[key] = this.escapeObjectRecursive(obj[key]);
+                }
+            }
+            return newObj;
+        }
+        return obj;
+    }
+
     /**
      * @inheritdoc
      */
@@ -24,7 +65,29 @@ class Telegram extends NotificationProvider {
             }
 
             if (notification.telegramUseTemplate) {
-                params.text = await this.renderTemplate(notification.telegramTemplate, msg, monitorJSON, heartbeatJSON);
+                let monitorJSONCopy = monitorJSON;
+                let heartbeatJSONCopy = heartbeatJSON;
+
+                if (notification.telegramTemplateParseMode === "MarkdownV2") {
+                    msg = this.escapeMarkdownV2(msg);
+
+                    if (monitorJSONCopy) {
+                        monitorJSONCopy = this.escapeObjectRecursive(monitorJSONCopy);
+                    } else {
+                        // for testing monitorJSON is null, provide escaped defaults
+                        monitorJSONCopy = {
+                            name: this.escapeMarkdownV2("Monitor Name not available"),
+                            hostname: this.escapeMarkdownV2("testing.hostname"),
+                            url: this.escapeMarkdownV2("testing.hostname"),
+                        };
+                    }
+
+                    if (heartbeatJSONCopy) {
+                        heartbeatJSONCopy = this.escapeObjectRecursive(heartbeatJSONCopy);
+                    }
+                }
+
+                params.text = await this.renderTemplate(notification.telegramTemplate, msg, monitorJSONCopy, heartbeatJSONCopy);
 
                 if (notification.telegramTemplateParseMode !== "plain") {
                     params.parse_mode = notification.telegramTemplateParseMode;