ProvenPin Install

xss HTML whitelist filter: working versions (tested 2026-10-16)

Filter untrusted HTML with xss using a safe tag whitelist, stripping scripts and event handlers while keeping safe markup offline.

passed5 passed · 0 failed2026-10-16 15:21 UTC
Status
passed
Last passed
2026-10-16 15:21 UTC
Tests
5 / 5
Language
TypeScript
Runtime
node v22.23.3
pinned versions3
xss@1.0.15@types/node@26.6.5tsx@4.23.15
run it
npm install --no-audit --no-fund --ignore-scripts=false
npm test
test environment
node v22.23.3
linux 6.17.0-1022-azure
x64
runner: github-actions 38923127324

The code

Exactly the files that passed. Your agent can pull them with get_recipe("xss-filter-html") (install), or see them on GitHub.

package.json
{
  "name": "xss-filter-html",
  "private": true,
  "type": "module",
  "scripts": {
    "test": "node --import tsx --test test/*.test.ts"
  },
  "dependencies": {
    "xss": "1.0.15"
  },
  "devDependencies": {
    "@types/node": "26.6.5",
    "tsx": "4.23.15"
  }
}
src/sanitize.ts
import xss from "xss";

export const safeTags: string[] = [
  "a",
  "b",
  "strong",
  "i",
  "em",
  "u",
  "p",
  "br",
  "ul",
  "ol",
  "li",
  "code",
  "pre",
  "blockquote",
  "h1",
  "h2",
  "h3",
];

export const whiteList: Record<string, string[]> = {
  a: ["href", "title"],
  b: [],
  strong: [],
  i: [],
  em: [],
  u: [],
  p: [],
  br: [],
  ul: [],
  ol: [],
  li: [],
  code: [],
  pre: [],
  blockquote: [],
  h1: [],
  h2: [],
  h3: [],
};

export function sanitizeHtml(input: string): string {
  return xss(input, {
    whiteList,
    stripIgnoreTag: true,
    stripIgnoreTagBody: ["script", "style"],
    allowCommentTag: false,
  });
}
test/sanitize.test.ts
import { test } from "node:test";
import assert from "node:assert/strict";
import { sanitizeHtml } from "../src/sanitize.ts";

test("keeps whitelisted markup intact", () => {
  const out = sanitizeHtml("<p>Hello <b>world</b> and <em>friends</em></p>");
  assert.equal(out, "<p>Hello <b>world</b> and <em>friends</em></p>");
});

test("strips script tags and their contents", () => {
  const out = sanitizeHtml("<p>ok</p><script>alert(1)</script>");
  assert.ok(out.includes("<p>ok</p>"));
  assert.ok(!out.toLowerCase().includes("<script"));
  assert.ok(!out.includes("alert(1)"));
});

test("removes event handler attributes but keeps safe ones", () => {
  const out = sanitizeHtml('<a href="https://example.com" onclick="alert(1)">link</a>');
  assert.ok(out.includes("https://example.com"));
  assert.ok(out.includes(">link</a>"));
  assert.ok(!out.toLowerCase().includes("onclick"));
  assert.ok(!out.includes("alert(1)"));
});

test("removes javascript: urls", () => {
  const out = sanitizeHtml('<a href="javascript:alert(1)">x</a>');
  assert.ok(!out.toLowerCase().includes("javascript:"));
  assert.ok(out.includes(">x</a>"));
});

test("strips disallowed tags and their handlers", () => {
  const out = sanitizeHtml('<img src=x onerror=alert(1)><iframe src="https://evil.example"></iframe>');
  assert.ok(!out.toLowerCase().includes("<img"));
  assert.ok(!out.toLowerCase().includes("<iframe"));
  assert.ok(!out.includes("onerror"));
  assert.ok(!out.includes("evil.example"));
});

Connect to ProvenPin

Add the free MCP server so your agent can pull this recipe and others like it. Same setup as the docs.

terminal
claude mcp add --transport http provenpin https://mcp.provenpin.com/mcp

Any other MCP client: Streamable HTTP at https://mcp.provenpin.com/mcp. No API key, no signup.