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fix(platform-browser): escape newlines in Meta selector values by rootvector2 · Pull Request #71236 · angular/angular · GitHub
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fix(platform-browser): escape newlines in Meta selector values #71236

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fix(platform-browser): escape newlines in Meta selector values #71236

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9 changes: 7 additions & 2 deletions packages/platform-browser/src/browser/meta.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -205,8 +205,13 @@ function parseSelector(tag: MetaDefinition): string {

function escapeSelectorValue(value: string): string {
// Escape backslashes and double quotes to prevent CSS selector injection.
// This securely confines the value inside an attribute selector.
return `"${value.replace(/\\/g, '\\\\').replace(/"/g, '\\"')}"`;
// This securely confines the value inside an attribute selector. A newline cannot be confined
// that way: it terminates the string token (CSS Syntax 3 4.3.5), and carriage return and form
// feed are preprocessed into one (CSS Syntax 3 3.3), so write those as character escapes.
return `"${value
.replace(/\\/g, '\\\\')
.replace(/"/g, '\\"')
.replace(/[\n\r\f]/g, (char) => `\\${char.charCodeAt(0).toString(16)} `)}"`;
}

function containsAttributes(tag: MetaDefinition, elem: HTMLMetaElement): boolean {
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19 changes: 19 additions & 0 deletions packages/platform-browser/test/browser/meta_spec.ts
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Expand Up @@ -244,6 +244,25 @@ describe('Meta service', () => {
metaService.removeTagElement(meta);
});

it('should escape newlines in selector values derived from the tag definition', () => {
// A raw newline terminates the CSS string token, so the derived `meta[name="..."]`
// selector is invalid and `querySelector` rejects it. Carriage return and form feed are
// preprocessed into a newline, so they behave the same way.
for (const name of ['description\nevil', 'description\revil', 'description\fevil']) {
const meta = metaService.addTag({name, content: 'first'})!;

expect(meta.getAttribute('name')).toEqual(name);
// Re-adding has to resolve the existing tag through the derived selector.
expect(metaService.addTag({name, content: 'first'})).toBe(meta);

metaService.updateTag({name, content: 'second'});
expect(meta.getAttribute('content')).toEqual('second');

// 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.
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