diff --git a/CHANGELOG.md b/CHANGELOG.md
index fe91e11e353..8c398d321f6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -180,6 +180,7 @@ Docs: https://docs.openclaw.ai
 - Providers/OpenRouter: gate Anthropic prompt-cache `cache_control` markers to native/default OpenRouter routes and preserve them for native OpenRouter hosts behind custom provider ids. Thanks @vincentkoc.
 - Browser/CDP: validate both initial and discovered CDP websocket endpoints before connect so strict SSRF policy blocks cross-host pivots and direct websocket targets. (#60469) Thanks @eleqtrizit.
 - Browser/profiles: reject remote browser profile `cdpUrl` values that violate strict SSRF policy before saving config, with clearer validation errors for blocked endpoints. (#60477) Thanks @eleqtrizit.
+- Mattermost/slash commands: harden native slash-command callback token validation to use constant-time secret comparison, matching the existing interaction-token path.
 
 ## 2026.4.1
 
diff --git a/extensions/mattermost/src/mattermost/slash-http.send-config.test.ts b/extensions/mattermost/src/mattermost/slash-http.send-config.test.ts
index a366572cd09..49877df3fb2 100644
--- a/extensions/mattermost/src/mattermost/slash-http.send-config.test.ts
+++ b/extensions/mattermost/src/mattermost/slash-http.send-config.test.ts
@@ -236,4 +236,29 @@ describe("slash-http cfg threading", () => {
       }),
     );
   });
+
+  it("does not rely on Set.has for command token validation", async () => {
+    const commandTokens = new Set(["valid-token"]);
+    const hasSpy = vi.fn(() => {
+      throw new Error("Set.has should not be used for slash token validation");
+    });
+    Object.defineProperty(commandTokens, "has", {
+      value: hasSpy,
+      configurable: true,
+    });
+
+    const handler = createSlashCommandHttpHandler({
+      account: accountFixture,
+      cfg: {} as OpenClawConfig,
+      runtime: {} as RuntimeEnv,
+      commandTokens,
+    });
+    const response = createResponse();
+
+    await handler(createRequest(), response.res);
+
+    expect(response.res.statusCode).toBe(200);
+    expect(response.getBody()).toContain("Processing");
+    expect(hasSpy).not.toHaveBeenCalled();
+  });
 });
diff --git a/extensions/mattermost/src/mattermost/slash-http.ts b/extensions/mattermost/src/mattermost/slash-http.ts
index 7fccd8ea4e7..9527549c23a 100644
--- a/extensions/mattermost/src/mattermost/slash-http.ts
+++ b/extensions/mattermost/src/mattermost/slash-http.ts
@@ -6,6 +6,7 @@
  */
 
 import type { IncomingMessage, ServerResponse } from "node:http";
+import { safeEqualSecret } from "openclaw/plugin-sdk/browser-support";
 import type { ResolvedMattermostAccount } from "../mattermost/accounts.js";
 import { getMattermostRuntime } from "../runtime.js";
 import {
@@ -78,6 +79,18 @@ function sendJsonResponse(
   res.end(JSON.stringify(body));
 }
 
+function matchesRegisteredCommandToken(
+  commandTokens: ReadonlySet<string>,
+  candidate: string,
+): boolean {
+  for (const token of commandTokens) {
+    if (safeEqualSecret(candidate, token)) {
+      return true;
+    }
+  }
+  return false;
+}
+
 type SlashInvocationAuth = {
   ok: boolean;
   denyResponse?: MattermostSlashCommandResponse;
@@ -242,7 +255,7 @@ export function createSlashCommandHttpHandler(params: SlashHttpHandlerParams) {
 
     // Validate token — fail closed: reject when no tokens are registered
     // (e.g. registration failed or startup was partial)
-    if (commandTokens.size === 0 || !commandTokens.has(payload.token)) {
+    if (commandTokens.size === 0 || !matchesRegisteredCommandToken(commandTokens, payload.token)) {
       sendJsonResponse(res, 401, {
         response_type: "ephemeral",
         text: "Unauthorized: invalid command token.",