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fix(core): sanitize meta selectors #68836

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fix(core): sanitize meta selectors #68836

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8a0047e
fix(core): sanitize meta selectors
JeanMeche May 20, 2026
c2dcf4e
fixup! fix(core): sanitize meta selectors
JeanMeche May 21, 2026
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17 changes: 14 additions & 3 deletions packages/platform-browser/src/browser/meta.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -102,7 +102,8 @@ export class Meta {
*/
getTag(attrSelector: string): HTMLMetaElement | null {
if (!attrSelector) return null;
return this._doc.querySelector(`meta[${attrSelector}]`) || null;
const meta = this._doc.querySelector(`meta[${attrSelector}]`);
return meta?.nodeName.toLowerCase() === 'meta' ? meta : null;
}

/**
Expand All @@ -114,7 +115,11 @@ export class Meta {
getTags(attrSelector: string): HTMLMetaElement[] {
if (!attrSelector) return [];
const list /*NodeList*/ = this._doc.querySelectorAll(`meta[${attrSelector}]`);
return list ? [].slice.call(list) : [];
return list
? (([].slice.call(list) as HTMLElement[]).filter(
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@alan-agius4 alan-agius4 May 21, 2026

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NIT:

Not sure why _doc in the constructor is any in this case, which does cause the need for castings.

Suggested change
? (([].slice.call(list) as HTMLElement[]).filter(
? ((Array.from(list) as HTMLElement[]).filter(

(elem) => elem.nodeName.toLowerCase() === 'meta',
) as HTMLMetaElement[])
: [];
}

/**
Expand Down Expand Up @@ -183,7 +188,13 @@ export class Meta {

private _parseSelector(tag: MetaDefinition): string {
const attr: string = tag.name ? 'name' : 'property';
return `${attr}="${tag[attr]}"`;
return `${attr}=${this._escapeSelectorValue(String(tag[attr]))}`;
}

private _escapeSelectorValue(value: string): string {
// Escape backslashes and double quotes to prevent CSS selector injection.
// This securely confines the value inside an attribute selector.
return `"${value.replace(/\\/g, '\\\\').replace(/"/g, '\\"')}"`;
}

private _containsAttributes(tag: MetaDefinition, elem: HTMLMetaElement): boolean {
Expand Down
55 changes: 55 additions & 0 deletions packages/platform-browser/test/browser/meta_spec.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -89,6 +89,24 @@ describe('Meta service', () => {
expect(actual!.getAttribute('content')).toEqual('4321');
});

it('should not allow a custom selector to match off target elements like the body tag', () => {
// This payload attempts to break out of the `meta[name="..."]` constraint entirely
// and inject a comma to target arbitrary DOM elements like the `body` tag via the
// `selector` argument of `updateTag`.
const attackerSelector = 'name="description"], body, meta[name="pwned"';

const firstMeta = metaService.updateTag({content: 'pwned'}, attackerSelector)!;

expect(firstMeta).not.toBeNull();
// It creates a new meta element instead of targeting `body` because it did not
// find a meta element matching the dirty selector since `body` is not a `meta` tag
expect(firstMeta!.nodeName.toLowerCase()).toEqual('meta');
expect(firstMeta!.getAttribute('content')).toEqual('pwned');
expect(doc.body.getAttribute('content')).toBeNull();

metaService.removeTagElement(firstMeta);
});

it('should extract selector from the tag definition', () => {
const selector = 'property="fb:app_id"';
metaService.updateTag({property: 'fb:app_id', content: '666'});
Expand Down Expand Up @@ -137,6 +155,43 @@ describe('Meta service', () => {
metaService.removeTagElement(actual);
});

it('should escape selector values when deriving the match selector', () => {
// This payload attempts to prematurely close the attribute selector
// and match another attribute.
const property = 'fb:app_id"][content="123456789';

const meta = metaService.updateTag({property, content: 'pwned'})!;

expect(meta).not.toBe(defaultMeta);
expect(meta.getAttribute('property')).toEqual(property);
expect(meta.getAttribute('content')).toEqual('pwned');
expect(metaService.getTags('property="fb:app_id"').length).toEqual(1);

// clean up
metaService.removeTagElement(meta);
});

it('should not let a quoted name break out of the meta selector and target body', () => {
// This payload attempts to break out of the `meta[name="..."]` constraint entirely
// and inject a comma to target arbitrary DOM elements like the `body` tag.
const attackerName = 'description"], body';

const firstMeta = metaService.addTag({name: attackerName, content: 'safe'})!;
const secondMeta = metaService.addTag({name: attackerName, content: 'safe'})!;

expect(firstMeta).toBe(secondMeta);
expect(firstMeta.tagName).toEqual('META');
expect(
Array.from(doc.getElementsByTagName('meta')).filter(
(meta) => meta.getAttribute('name') === attackerName,
).length,
).toEqual(1);
expect(doc.body).not.toBeNull();

// clean up
metaService.removeTagElement(firstMeta);
});

it('should add multiple new meta tags', () => {
const nameSelector = 'name="twitter:title"';
const propertySelector = 'property="og:title"';
Expand Down
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