fix: check plugin http.post url against origin and add regression tests

lib/__tests__/plugin-api.test.ts

@@ -148,3 +148,46 @@ describe('toast bridge', () => {
     expect(api.toast.warning).toBeInstanceOf(Function);
   });
 });
+
+describe('http.post path validation', () => {
+  function makeApi(permissions: string[] = ['http:post']) {
+    return createPluginAPI(makePlugin({ permissions }));
+  }
+
+  it('rejects protocol-relative URLs like //evil.example', async () => {
+    const api = makeApi();
+    await expect(api.http.post('//evil.example/collect', {})).rejects.toThrow('must start with /api/');
+  });
+
+  it('rejects absolute URLs to other origins', async () => {
+    const api = makeApi();
+    await expect(api.http.post('https://evil.example/steal', {})).rejects.toThrow('must start with /api/');
+  });
+
+  it('rejects paths not under /api/', async () => {
+    const api = makeApi();
+    await expect(api.http.post('/other/path', {})).rejects.toThrow('must start with /api/');
+  });
+
+  it('rejects paths that use backslash to bypass the check', async () => {
+    const api = makeApi();
+    await expect(api.http.post('/api/\\@evil.example', {})).rejects.toThrow();
+  });
+
+  it('throws without http:post permission', async () => {
+    const api = makeApi([]);
+    await expect(api.http.post('/api/jitsi', {})).rejects.toThrow('lacks permission');
+  });
+
+  it('accepts a valid /api/ path', async () => {
+    const api = makeApi();
+    globalThis.fetch = vi.fn().mockResolvedValue({
+      ok: true,
+      status: 200,
+      json: () => Promise.resolve({ url: 'https://meet.example.com/room' }),
+    });
+    const result = await api.http.post('/api/jitsi', { eventTitle: 'test' });
+    expect(result.ok).toBe(true);
+    expect(result.data).toEqual({ url: 'https://meet.example.com/room' });
+  });
+});

lib/plugin-api.ts

@@ -647,8 +647,12 @@ export function createPluginAPI(plugin: InstalledPlugin): PluginAPI {
     http: {
       post: async (path: string, body: Record<string, unknown>) => {
         requirePermission(plugin, 'http:post');
-        if (typeof path !== 'string' || !path.startsWith('/')) {
-          throw new Error('path must be an absolute path starting with /');
+        if (typeof path !== 'string' || !path.startsWith('/api/')) {
+          throw new Error('path must start with /api/');
+        }
+        const url = new URL(path, globalThis.location.origin);
+        if (url.origin !== globalThis.location.origin) {
+          throw new Error('path must resolve to the same origin');
         }
         const { client } = useAuthStore.getState();
         const headers: Record<string, string> = { 'Content-Type': 'application/json' };
@@ -656,7 +660,7 @@ export function createPluginAPI(plugin: InstalledPlugin): PluginAPI {
           headers['Authorization'] = client.getAuthHeader();
           headers['X-JMAP-Username'] = client.getUsername();
         }
-        const res = await fetch(path, {
+        const res = await fetch(url.pathname + url.search, {
           method: 'POST',
           headers,
           body: JSON.stringify(body),