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🔐 Refactor MetaTagInjector and tests for security, structure & maintainability #7896

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200ee58
Refactor MetaTagInjector tests for clarity, efficiency & security 🧿
Krishprajapati15 May 8, 2025
69b8103
Refactor MetaTagInjector for security, clarity, and maintainability
Krishprajapati15 May 8, 2025
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163 changes: 82 additions & 81 deletions apps/web/functions/components/metaTagInjector.test.ts
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Original file line number Diff line number Diff line change
@@ -1,93 +1,94 @@
import { MetaTagInjector } from './metaTagInjector'

test('should append meta tag to element', () => {
const element = {
append: jest.fn(),
} as unknown as Element
const property = 'property'
const content = 'content'
const injector = new MetaTagInjector(
{
title: 'test',
url: 'testUrl',
image: 'testImage',
description: 'testDescription',
},
new Request('http://localhost'),
)
injector.appendProperty(element, property, content)
expect(element.append).toHaveBeenCalledWith(`<meta property="${property}" content="${content}" data-rh="true">`, {
html: true,
})
describe('MetaTagInjector', () => {
let element: HTMLElement
let injector: MetaTagInjector

injector.element(element)
expect(element.append).toHaveBeenCalledWith(`<meta property="og:title" content="test" data-rh="true">`, {
html: true,
})
expect(element.append).toHaveBeenCalledWith(`<meta name="description" content="testDescription" data-rh="true">`, {
html: true,
})
expect(element.append).toHaveBeenCalledWith(
`<meta property="og:description" content="testDescription" data-rh="true">`,
{
html: true,
},
)
expect(element.append).toHaveBeenCalledWith(`<meta property="og:image" content="testImage" data-rh="true">`, {
html: true,
})
expect(element.append).toHaveBeenCalledWith(`<meta property="og:image:width" content="1200" data-rh="true">`, {
html: true,
})
expect(element.append).toHaveBeenCalledWith(`<meta property="og:image:height" content="630" data-rh="true">`, {
html: true,
})
expect(element.append).toHaveBeenCalledWith(`<meta property="og:image:alt" content="test" data-rh="true">`, {
html: true,
})
expect(element.append).toHaveBeenCalledWith(`<meta property="og:type" content="website" data-rh="true">`, {
html: true,
})
expect(element.append).toHaveBeenCalledWith(`<meta property="og:url" content="testUrl" data-rh="true">`, {
html: true,
const metaData = {
title: 'test',
url: 'testUrl',
image: 'testImage',
description: 'testDescription',
}

beforeEach(() => {
element = {
append: jest.fn(),
} as unknown as HTMLElement

injector = new MetaTagInjector(metaData, new Request('http://localhost'))
})

expect(element.append).toHaveBeenCalledWith(
`<meta property="twitter:card" content="summary_large_image" data-rh="true">`,
{
html: true,
},
)
expect(element.append).toHaveBeenCalledWith(`<meta property="twitter:title" content="test" data-rh="true">`, {
html: true,
test('should append individual meta tag correctly', () => {
const property = 'property'
const content = 'content'

injector.appendProperty(element, property, content)

expect(element.append).toHaveBeenCalledWith(
`<meta property="${property}" content="${content}" data-rh="true">`,
{ html: true }
)
})
expect(element.append).toHaveBeenCalledWith(`<meta property="twitter:image" content="testImage" data-rh="true">`, {
html: true,

test('should append all required meta tags to the element', () => {
injector.element(element)

const expectedTags = [
`<meta property="og:title" content="test" data-rh="true">`,
`<meta name="description" content="testDescription" data-rh="true">`,
`<meta property="og:description" content="testDescription" data-rh="true">`,
`<meta property="og:image" content="testImage" data-rh="true">`,
`<meta property="og:image:width" content="1200" data-rh="true">`,
`<meta property="og:image:height" content="630" data-rh="true">`,
`<meta property="og:image:alt" content="test" data-rh="true">`,
`<meta property="og:type" content="website" data-rh="true">`,
`<meta property="og:url" content="testUrl" data-rh="true">`,
`<meta property="twitter:card" content="summary_large_image" data-rh="true">`,
`<meta property="twitter:title" content="test" data-rh="true">`,
`<meta property="twitter:image" content="testImage" data-rh="true">`,
`<meta property="twitter:image:alt" content="test" data-rh="true">`,
]

expectedTags.forEach((tag) => {
expect(element.append).toHaveBeenCalledWith(tag, { html: true })
})

expect(element.append).toHaveBeenCalledTimes(expectedTags.length)
})
expect(element.append).toHaveBeenCalledWith(`<meta property="twitter:image:alt" content="test" data-rh="true">`, {
html: true,

test('should append x-blocked-paths meta if present in headers', () => {
const blockedRequest = new Request('http://localhost')
blockedRequest.headers.set('x-blocked-paths', '/')
const blockedInjector = new MetaTagInjector(metaData, blockedRequest)

blockedInjector.element(element)

expect(element.append).toHaveBeenCalledWith(
`<meta property="x:blocked-paths" content="/" data-rh="true">`,
{ html: true }
)
})

expect(element.append).toHaveBeenCalledTimes(14)
})
test('should prevent potential XSS via meta content', () => {
const unsafeMetaData = {
title: `<script>alert("xss")</script>`,
url: 'https://safe.com',
image: 'img.jpg',
description: 'test',
}

const xssInjector = new MetaTagInjector(unsafeMetaData, new Request('http://localhost'))
const xssElement = {
append: jest.fn(),
} as unknown as HTMLElement

xssInjector.element(xssElement)

// Assert it does not include unescaped script tag
const calls = (xssElement.append as jest.Mock).mock.calls
const scriptInjectionDetected = calls.some(([tag]) => tag.includes('<script>'))

test('should pass through header blocked paths', () => {
const element = {
append: jest.fn(),
} as unknown as Element
const request = new Request('http://localhost')
request.headers.set('x-blocked-paths', '/')
const injector = new MetaTagInjector(
{
title: 'test',
url: 'testUrl',
image: 'testImage',
description: 'testDescription',
},
request,
)
injector.element(element)
expect(element.append).toHaveBeenCalledWith(`<meta property="x:blocked-paths" content="/" data-rh="true">`, {
html: true,
expect(scriptInjectionDetected).toBe(false)
})
})
82 changes: 54 additions & 28 deletions apps/web/functions/components/metaTagInjector.ts
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Original file line number Diff line number Diff line change
@@ -1,52 +1,78 @@
import { MetaTagInjectorInput } from 'shared-cloud/metatags'

/**
* Listener class for Cloudflare's HTMLRewriter {@link https://developers.cloudflare.com/workers/runtime-apis/html-rewriter}
* to inject meta tags into the <head> of an HTML document.
* Injects meta tags into the <head> element using Cloudflare's HTMLRewriter.
* @see https://developers.cloudflare.com/workers/runtime-apis/html-rewriter
*/
export class MetaTagInjector implements HTMLRewriterElementContentHandlers {
static SELECTOR = 'head'

constructor(
private input: MetaTagInjectorInput,
private request: Request,
private readonly input: MetaTagInjectorInput,
private readonly request: Request,
) {}

append(element: Element, attribute: string, content: string) {
// without adding data-rh="true", react-helmet-async doesn't overwrite existing metatags
element.append(`<meta ${attribute} content="${content}" data-rh="true">`, { html: true })
/**
* Appends a meta tag to the element.
* @param element - The HTML element to append to.
* @param attribute - Meta tag attribute (e.g., property="og:title").
* @param content - Meta tag content.
*/
private append(element: Element, attribute: string, content: string) {
const safeContent = this.escape(content)
element.append(`<meta ${attribute} content="${safeContent}" data-rh="true">`, { html: true })
}

appendProperty(element: Element, property: string, content: string) {
this.append(element, `property="${property}"`, content)
/**
* Appends a property-based meta tag.
* @param element - The HTML element to append to.
* @param property - The OpenGraph or Twitter meta property.
* @param content - The content of the property.
*/
private appendProperty(element: Element, property: string, content: string) {
if (content) {
this.append(element, `property="${property}"`, content)
}
}

element(element: Element) {
if (this.input.description) {
this.append(element, `name="description"`, this.input.description)
}
/**
* Escapes special HTML characters in content.
*/
private escape(str: string): string {
return str
.replace(/&/g, '&amp;')
.replace(/"/g, '&quot;')
.replace(/</g, '&lt;')
.replace(/>/g, '&gt;')
}

//Open Graph Tags
this.appendProperty(element, 'og:title', this.input.title)
if (this.input.description) {
this.appendProperty(element, 'og:description', this.input.description)
/**
* Injects all required meta tags into the <head> of the HTML document.
*/
element(element: Element): void {
const { title, description, image, url } = this.input

if (description) {
this.append(element, 'name="description"', description)
this.appendProperty(element, 'og:description', description)
}
if (this.input.image) {
this.appendProperty(element, 'og:image', this.input.image)

this.appendProperty(element, 'og:title', title)
this.appendProperty(element, 'og:type', 'website')
this.appendProperty(element, 'og:url', url)

if (image) {
this.appendProperty(element, 'og:image', image)
this.appendProperty(element, 'og:image:width', '1200')
this.appendProperty(element, 'og:image:height', '630')
this.appendProperty(element, 'og:image:alt', this.input.title)
this.appendProperty(element, 'og:image:alt', title)

this.appendProperty(element, 'twitter:image', image)
this.appendProperty(element, 'twitter:image:alt', title)
}
this.appendProperty(element, 'og:type', 'website')
this.appendProperty(element, 'og:url', this.input.url)

//Twitter Tags
this.appendProperty(element, 'twitter:card', 'summary_large_image')
this.appendProperty(element, 'twitter:title', this.input.title)
if (this.input.image) {
this.appendProperty(element, 'twitter:image', this.input.image)
this.appendProperty(element, 'twitter:image:alt', this.input.title)
}
this.appendProperty(element, 'twitter:title', title)

const blockedPaths = this.request.headers.get('x-blocked-paths')
if (blockedPaths) {
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