1501642 - DOMParser processes HTML tags inside CSS comments

Status: RESOLVED INVALID

(Core :: DOM: Core & HTML, defect)

Description

[Andrew Jarvis]

Attachment: DOMParserBug.html

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:63.0) Gecko/20100101 Firefox/63.0

Steps to reproduce:

Load the attached HTML file into the browser.
The embedded script calls DOMParser with HTML containing a style sheet definition.
The style sheet has a </style> end tag in a comment.


Actual results:

The </style> end tag within the comment prematurely terminated parsing of the style sheet so the alert box shows 'Number of rules: 1'


Expected results:

The alert box should show 'Number of rules: 2'

Comment 1

[Damira Akh]

Reproducible. 

Build ID 	20181029100347
User Agent 	Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:65.0) Gecko/20100101 Firefox/65.0

I go a little bit further and tested it in Chrome and IE

Google Chrome: did not show up anything
IE: Same outcome as in Firefox.

Comment 2

[Emilio Cobos Álvarez [:emilio]]

(In reply to Andrew Jarvis from comment #0)
> Expected results:
> 
> The alert box should show 'Number of rules: 2'

What spec says that? Firefox / Edge looks correct to me, I don't know why the HTML parser would need to know CSS comment syntax.

Blink / WebKit also agrees on just one style sheet, just doesn't let you access it via document.styleSheets, which I guess is wrong.

HTML-parsing wise all browsers seem consistent, so I'm pretty sure this is invalid, but I've cc'd some folks that can correct me if I'm wrong.

Comment 3

[Boris Zbarsky [:bzbarsky]]

You're not wrong.  </style> terminates <style>.  That determination happens before any parsing of the sheet even starts.   The string determined by that is then passed to the CSS parser.

Comment 4

[Xidorn Quan [:xidorn] UTC+10]

FWIW, this behavior is well-specced in the HTML spec: https://html.spec.whatwg.org/multipage/parsing.html#parsing-html-fragments

It clearly shows that HTML parser would treat content inside <style> as raw text, and ends it whenever </style> is found.