Escape HTML from messages in error page (#4430)

Co-authored-by: Asher <ash@coder.com>
Co-authored-by: Joe Previte <jjprevite@gmail.com>

test/unit/node/routes/errors.test.ts

@@ -0,0 +1,35 @@
+import express from "express"
+import { errorHandler } from "../../../../src/node/routes/errors"
+
+describe("error page is rendered for text/html requests", () => {
+  it("escapes any html in the error messages", async () => {
+    const next = jest.fn()
+    const err = {
+      code: "ENOENT",
+      statusCode: 404,
+      message: ";>hello<script>alert(1)</script>",
+    }
+    const req = createRequest()
+    const res = {
+      status: jest.fn().mockReturnValue(this),
+      send: jest.fn().mockReturnValue(this),
+      set: jest.fn().mockReturnValue(this),
+    } as unknown as express.Response
+
+    await errorHandler(err, req, res, next)
+    expect(res.status).toHaveBeenCalledWith(404)
+    expect(res.send).toHaveBeenCalledWith(expect.not.stringContaining("<script>"))
+  })
+})
+
+function createRequest(): express.Request {
+  return {
+    headers: {
+      accept: ["text/html"],
+    },
+    originalUrl: "http://example.com/test",
+    query: {
+      to: "test",
+    },
+  } as unknown as express.Request
+}