diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9c274f7577..9ef3d0074e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -29,7 +29,7 @@ Docs: https://docs.openclaw.ai
 - Web UI: resolve header logo path when `gateway.controlUi.basePath` is set. (#7178) Thanks @Yeom-JinHo.
 - Web UI: apply button styling to the new-messages indicator.
 - Security: keep untrusted channel metadata out of system prompts (Slack/Discord). Thanks @KonstantinMirin.
-- Security: require explicit credentials for gateway URL overrides to prevent credential leakage. (#8113) Thanks @victormier.
+- Security: enforce sandboxed media paths for message tool attachments. (#9182) Thanks @victormier.
 - Voice call: harden webhook verification with host allowlists/proxy trust and keep ngrok loopback bypass.
 - Cron: accept epoch timestamps and 0ms durations in CLI `--at` parsing.
 - Cron: reload store data when the store file is recreated or mtime changes.
diff --git a/src/agents/sandbox-paths.ts b/src/agents/sandbox-paths.ts
index 054a16a689..22c72947a5 100644
--- a/src/agents/sandbox-paths.ts
+++ b/src/agents/sandbox-paths.ts
@@ -1,8 +1,11 @@
 import fs from "node:fs/promises";
 import os from "node:os";
 import path from "node:path";
+import { fileURLToPath } from "node:url";
 
 const UNICODE_SPACES = /[\u00A0\u2000-\u200A\u202F\u205F\u3000]/g;
+const HTTP_URL_RE = /^https?:\/\//i;
+const DATA_URL_RE = /^data:/i;
 
 function normalizeUnicodeSpaces(str: string): string {
   return str.replace(UNICODE_SPACES, " ");
@@ -49,6 +52,40 @@ export async function assertSandboxPath(params: { filePath: string; cwd: string;
   return resolved;
 }
 
+export function assertMediaNotDataUrl(media: string): void {
+  const raw = media.trim();
+  if (DATA_URL_RE.test(raw)) {
+    throw new Error("data: URLs are not supported for media. Use buffer instead.");
+  }
+}
+
+export async function resolveSandboxedMediaSource(params: {
+  media: string;
+  sandboxRoot: string;
+}): Promise<string> {
+  const raw = params.media.trim();
+  if (!raw) {
+    return raw;
+  }
+  if (HTTP_URL_RE.test(raw)) {
+    return raw;
+  }
+  let candidate = raw;
+  if (/^file:\/\//i.test(candidate)) {
+    try {
+      candidate = fileURLToPath(candidate);
+    } catch {
+      throw new Error(`Invalid file:// URL for sandboxed media: ${raw}`);
+    }
+  }
+  const resolved = await assertSandboxPath({
+    filePath: candidate,
+    cwd: params.sandboxRoot,
+    root: params.sandboxRoot,
+  });
+  return resolved.resolved;
+}
+
 async function assertNoSymlink(relative: string, root: string) {
   if (!relative) {
     return;
diff --git a/src/agents/tools/message-tool.test.ts b/src/agents/tools/message-tool.test.ts
index 15d416fd89..a289908ac1 100644
--- a/src/agents/tools/message-tool.test.ts
+++ b/src/agents/tools/message-tool.test.ts
@@ -1,6 +1,3 @@
-import fs from "node:fs/promises";
-import os from "node:os";
-import path from "node:path";
 import { describe, expect, it, vi } from "vitest";
 import type { ChannelPlugin } from "../../channels/plugins/types.js";
 import type { MessageActionRunResult } from "../../infra/outbound/message-action-runner.js";
@@ -165,50 +162,8 @@ describe("message tool description", () => {
   });
 });
 
-describe("message tool sandbox path validation", () => {
-  it("rejects filePath that escapes sandbox root", async () => {
-    const sandboxDir = await fs.mkdtemp(path.join(os.tmpdir(), "msg-sandbox-"));
-    try {
-      const tool = createMessageTool({
-        config: {} as never,
-        sandboxRoot: sandboxDir,
-      });
-
-      await expect(
-        tool.execute("1", {
-          action: "send",
-          target: "telegram:123",
-          filePath: "/etc/passwd",
-          message: "",
-        }),
-      ).rejects.toThrow(/sandbox/i);
-    } finally {
-      await fs.rm(sandboxDir, { recursive: true, force: true });
-    }
-  });
-
-  it("rejects path param with traversal sequence", async () => {
-    const sandboxDir = await fs.mkdtemp(path.join(os.tmpdir(), "msg-sandbox-"));
-    try {
-      const tool = createMessageTool({
-        config: {} as never,
-        sandboxRoot: sandboxDir,
-      });
-
-      await expect(
-        tool.execute("1", {
-          action: "send",
-          target: "telegram:123",
-          path: "../../../etc/shadow",
-          message: "",
-        }),
-      ).rejects.toThrow(/sandbox/i);
-    } finally {
-      await fs.rm(sandboxDir, { recursive: true, force: true });
-    }
-  });
-
-  it("allows filePath inside sandbox root", async () => {
+describe("message tool sandbox passthrough", () => {
+  it("forwards sandboxRoot to runMessageAction", async () => {
     mocks.runMessageAction.mockClear();
     mocks.runMessageAction.mockResolvedValue({
       kind: "send",
@@ -220,27 +175,22 @@ describe("message tool sandbox path validation", () => {
       dryRun: true,
     } satisfies MessageActionRunResult);
 
-    const sandboxDir = await fs.mkdtemp(path.join(os.tmpdir(), "msg-sandbox-"));
-    try {
-      const tool = createMessageTool({
-        config: {} as never,
-        sandboxRoot: sandboxDir,
-      });
+    const tool = createMessageTool({
+      config: {} as never,
+      sandboxRoot: "/tmp/sandbox",
+    });
 
-      await tool.execute("1", {
-        action: "send",
-        target: "telegram:123",
-        filePath: "./data/file.txt",
-        message: "",
-      });
+    await tool.execute("1", {
+      action: "send",
+      target: "telegram:123",
+      message: "",
+    });
 
-      expect(mocks.runMessageAction).toHaveBeenCalledTimes(1);
-    } finally {
-      await fs.rm(sandboxDir, { recursive: true, force: true });
-    }
+    const call = mocks.runMessageAction.mock.calls[0]?.[0];
+    expect(call?.sandboxRoot).toBe("/tmp/sandbox");
   });
 
-  it("skips validation when no sandboxRoot is set", async () => {
+  it("omits sandboxRoot when not configured", async () => {
     mocks.runMessageAction.mockClear();
     mocks.runMessageAction.mockResolvedValue({
       kind: "send",
@@ -259,11 +209,10 @@ describe("message tool sandbox path validation", () => {
     await tool.execute("1", {
       action: "send",
       target: "telegram:123",
-      filePath: "/etc/passwd",
       message: "",
     });
 
-    // Without sandboxRoot the validation is skipped — unsandboxed sessions work normally.
-    expect(mocks.runMessageAction).toHaveBeenCalledTimes(1);
+    const call = mocks.runMessageAction.mock.calls[0]?.[0];
+    expect(call?.sandboxRoot).toBeUndefined();
   });
 });
diff --git a/src/agents/tools/message-tool.ts b/src/agents/tools/message-tool.ts
index 9a8d3ab63a..aec6d9d050 100644
--- a/src/agents/tools/message-tool.ts
+++ b/src/agents/tools/message-tool.ts
@@ -19,7 +19,6 @@ import { normalizeAccountId } from "../../routing/session-key.js";
 import { normalizeMessageChannel } from "../../utils/message-channel.js";
 import { resolveSessionAgentId } from "../agent-scope.js";
 import { listChannelSupportedActions } from "../channel-tools.js";
-import { assertSandboxPath } from "../sandbox-paths.js";
 import { channelTargetSchema, channelTargetsSchema, stringEnum } from "../schema/typebox.js";
 import { jsonResult, readNumberParam, readStringParam } from "./common.js";
 
@@ -422,17 +421,6 @@ export function createMessageTool(options?: MessageToolOptions): AnyAgentTool {
         }
       }
 
-      // Validate file paths against sandbox root to prevent host file access.
-      const sandboxRoot = options?.sandboxRoot;
-      if (sandboxRoot) {
-        for (const key of ["filePath", "path"] as const) {
-          const raw = readStringParam(params, key, { trim: false });
-          if (raw) {
-            await assertSandboxPath({ filePath: raw, cwd: sandboxRoot, root: sandboxRoot });
-          }
-        }
-      }
-
       const accountId = readStringParam(params, "accountId") ?? agentAccountId;
       if (accountId) {
         params.accountId = accountId;
@@ -475,6 +463,7 @@ export function createMessageTool(options?: MessageToolOptions): AnyAgentTool {
         agentId: options?.agentSessionKey
           ? resolveSessionAgentId({ sessionKey: options.agentSessionKey, config: cfg })
           : undefined,
+        sandboxRoot: options?.sandboxRoot,
         abortSignal: signal,
       });
 
diff --git a/src/infra/outbound/message-action-runner.test.ts b/src/infra/outbound/message-action-runner.test.ts
index ed432b0704..5ca3a56436 100644
--- a/src/infra/outbound/message-action-runner.test.ts
+++ b/src/infra/outbound/message-action-runner.test.ts
@@ -1,3 +1,6 @@
+import fs from "node:fs/promises";
+import os from "node:os";
+import path from "node:path";
 import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 import type { ChannelPlugin } from "../../channels/plugins/types.js";
 import type { OpenClawConfig } from "../../config/config.js";
@@ -446,6 +449,164 @@ describe("runMessageAction sendAttachment hydration", () => {
       Buffer.from("hello").toString("base64"),
     );
   });
+
+  it("rewrites sandboxed media paths for sendAttachment", async () => {
+    const cfg = {
+      channels: {
+        bluebubbles: {
+          enabled: true,
+          serverUrl: "http://localhost:1234",
+          password: "test-password",
+        },
+      },
+    } as OpenClawConfig;
+    const sandboxDir = await fs.mkdtemp(path.join(os.tmpdir(), "msg-sandbox-"));
+    try {
+      await runMessageAction({
+        cfg,
+        action: "sendAttachment",
+        params: {
+          channel: "bluebubbles",
+          target: "+15551234567",
+          media: "./data/pic.png",
+          message: "caption",
+        },
+        sandboxRoot: sandboxDir,
+      });
+
+      const call = vi.mocked(loadWebMedia).mock.calls[0];
+      expect(call?.[0]).toBe(path.join(sandboxDir, "data", "pic.png"));
+    } finally {
+      await fs.rm(sandboxDir, { recursive: true, force: true });
+    }
+  });
+});
+
+describe("runMessageAction sandboxed media validation", () => {
+  beforeEach(async () => {
+    const { createPluginRuntime } = await import("../../plugins/runtime/index.js");
+    const { setSlackRuntime } = await import("../../../extensions/slack/src/runtime.js");
+    const runtime = createPluginRuntime();
+    setSlackRuntime(runtime);
+    setActivePluginRegistry(
+      createTestRegistry([
+        {
+          pluginId: "slack",
+          source: "test",
+          plugin: slackPlugin,
+        },
+      ]),
+    );
+  });
+
+  afterEach(() => {
+    setActivePluginRegistry(createTestRegistry([]));
+  });
+
+  it("rejects media outside the sandbox root", async () => {
+    const sandboxDir = await fs.mkdtemp(path.join(os.tmpdir(), "msg-sandbox-"));
+    try {
+      await expect(
+        runMessageAction({
+          cfg: slackConfig,
+          action: "send",
+          params: {
+            channel: "slack",
+            target: "#C12345678",
+            media: "/etc/passwd",
+            message: "",
+          },
+          sandboxRoot: sandboxDir,
+          dryRun: true,
+        }),
+      ).rejects.toThrow(/sandbox/i);
+    } finally {
+      await fs.rm(sandboxDir, { recursive: true, force: true });
+    }
+  });
+
+  it("rejects file:// media outside the sandbox root", async () => {
+    const sandboxDir = await fs.mkdtemp(path.join(os.tmpdir(), "msg-sandbox-"));
+    try {
+      await expect(
+        runMessageAction({
+          cfg: slackConfig,
+          action: "send",
+          params: {
+            channel: "slack",
+            target: "#C12345678",
+            media: "file:///etc/passwd",
+            message: "",
+          },
+          sandboxRoot: sandboxDir,
+          dryRun: true,
+        }),
+      ).rejects.toThrow(/sandbox/i);
+    } finally {
+      await fs.rm(sandboxDir, { recursive: true, force: true });
+    }
+  });
+
+  it("rewrites sandbox-relative media paths", async () => {
+    const sandboxDir = await fs.mkdtemp(path.join(os.tmpdir(), "msg-sandbox-"));
+    try {
+      const result = await runMessageAction({
+        cfg: slackConfig,
+        action: "send",
+        params: {
+          channel: "slack",
+          target: "#C12345678",
+          media: "./data/file.txt",
+          message: "",
+        },
+        sandboxRoot: sandboxDir,
+        dryRun: true,
+      });
+
+      expect(result.kind).toBe("send");
+      expect(result.sendResult?.mediaUrl).toBe(path.join(sandboxDir, "data", "file.txt"));
+    } finally {
+      await fs.rm(sandboxDir, { recursive: true, force: true });
+    }
+  });
+
+  it("rewrites MEDIA directives under sandbox", async () => {
+    const sandboxDir = await fs.mkdtemp(path.join(os.tmpdir(), "msg-sandbox-"));
+    try {
+      const result = await runMessageAction({
+        cfg: slackConfig,
+        action: "send",
+        params: {
+          channel: "slack",
+          target: "#C12345678",
+          message: "Hello\\nMEDIA: ./data/note.ogg",
+        },
+        sandboxRoot: sandboxDir,
+        dryRun: true,
+      });
+
+      expect(result.kind).toBe("send");
+      expect(result.sendResult?.mediaUrl).toBe(path.join(sandboxDir, "data", "note.ogg"));
+    } finally {
+      await fs.rm(sandboxDir, { recursive: true, force: true });
+    }
+  });
+
+  it("rejects data URLs in media params", async () => {
+    await expect(
+      runMessageAction({
+        cfg: slackConfig,
+        action: "send",
+        params: {
+          channel: "slack",
+          target: "#C12345678",
+          media: "data:image/png;base64,abcd",
+          message: "",
+        },
+        dryRun: true,
+      }),
+    ).rejects.toThrow(/data:/i);
+  });
 });
 
 describe("runMessageAction accountId defaults", () => {
diff --git a/src/infra/outbound/message-action-runner.ts b/src/infra/outbound/message-action-runner.ts
index e19ae85288..bc4ae734ff 100644
--- a/src/infra/outbound/message-action-runner.ts
+++ b/src/infra/outbound/message-action-runner.ts
@@ -10,6 +10,7 @@ import type { OpenClawConfig } from "../../config/config.js";
 import type { OutboundSendDeps } from "./deliver.js";
 import type { MessagePollResult, MessageSendResult } from "./message.js";
 import { resolveSessionAgentId } from "../../agents/agent-scope.js";
+import { assertMediaNotDataUrl, resolveSandboxedMediaSource } from "../../agents/sandbox-paths.js";
 import {
   readNumberParam,
   readStringArrayParam,
@@ -62,6 +63,7 @@ export type RunMessageActionParams = {
   deps?: OutboundSendDeps;
   sessionKey?: string;
   agentId?: string;
+  sandboxRoot?: string;
   dryRun?: boolean;
   abortSignal?: AbortSignal;
 };
@@ -326,6 +328,53 @@ function normalizeBase64Payload(params: { base64?: string; contentType?: string
   };
 }
 
+async function normalizeSandboxMediaParams(params: {
+  args: Record<string, unknown>;
+  sandboxRoot?: string;
+}): Promise<void> {
+  const sandboxRoot = params.sandboxRoot?.trim();
+  const mediaKeys: Array<"media" | "path" | "filePath"> = ["media", "path", "filePath"];
+  for (const key of mediaKeys) {
+    const raw = readStringParam(params.args, key, { trim: false });
+    if (!raw) {
+      continue;
+    }
+    assertMediaNotDataUrl(raw);
+    if (!sandboxRoot) {
+      continue;
+    }
+    const normalized = await resolveSandboxedMediaSource({ media: raw, sandboxRoot });
+    if (normalized !== raw) {
+      params.args[key] = normalized;
+    }
+  }
+}
+
+async function normalizeSandboxMediaList(params: {
+  values: string[];
+  sandboxRoot?: string;
+}): Promise<string[]> {
+  const sandboxRoot = params.sandboxRoot?.trim();
+  const normalized: string[] = [];
+  const seen = new Set<string>();
+  for (const value of params.values) {
+    const raw = value?.trim();
+    if (!raw) {
+      continue;
+    }
+    assertMediaNotDataUrl(raw);
+    const resolved = sandboxRoot
+      ? await resolveSandboxedMediaSource({ media: raw, sandboxRoot })
+      : raw;
+    if (seen.has(resolved)) {
+      continue;
+    }
+    seen.add(resolved);
+    normalized.push(resolved);
+  }
+  return normalized;
+}
+
 async function hydrateSetGroupIconParams(params: {
   cfg: OpenClawConfig;
   channel: ChannelId;
@@ -699,6 +748,14 @@ async function handleSendAction(ctx: ResolvedActionContext): Promise<MessageActi
     pushMedia(url);
   }
   pushMedia(parsed.mediaUrl);
+
+  const normalizedMediaUrls = await normalizeSandboxMediaList({
+    values: mergedMediaUrls,
+    sandboxRoot: input.sandboxRoot,
+  });
+  mergedMediaUrls.length = 0;
+  mergedMediaUrls.push(...normalizedMediaUrls);
+
   message = parsed.text;
   params.message = message;
   if (!params.replyTo && parsed.replyToId) {
@@ -967,6 +1024,11 @@ export async function runMessageAction(
   }
   const dryRun = Boolean(input.dryRun ?? readBooleanParam(params, "dryRun"));
 
+  await normalizeSandboxMediaParams({
+    args: params,
+    sandboxRoot: input.sandboxRoot,
+  });
+
   await hydrateSendAttachmentParams({
     cfg,
     channel,