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To: Sara Golemon <pollita@php.net>
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Content-Type: multipart/alternative; boundary=001a1136dfc6bbb0c104f1640cfc
Subject: Re: [PHP-DEV] [RFC] Improve HTML escape
From: yohgaki@ohgaki.net (Yasuo Ohgaki)

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Content-Type: text/plain; charset=UTF-8

Hi Sara,

On Sun, Feb 2, 2014 at 12:15 PM, Sara Golemon <pollita@php.net> wrote:

> On Sat, Feb 1, 2014 at 7:09 PM, Yasuo Ohgaki <yohgaki@ohgaki.net> wrote:
> > This is a little improvement for HTML escape.
> > https://wiki.php.net/rfc/secure-html-escape
> >
> > "/" escape is recommended by OWASP and we may follow them.
> >
> Could you include some samples of malicious input and what the output
> would actually look like?  It's not obvious from the RFC or the link
> referenced.


They don't explain as code. AFAIK This is the case for generating invalid
HTML that destroys HTML tag structure.

<tag attr=<?php htmlentities($str, ENT_QUOTES, 'UTF-8') ?>>

When $str is

sometext /

Produced HTML would be

<tag attr=sometext />

and tag is closed.

The code is broken in first place since attribute must be enclosed by
"(HTML5/XHTML) or '(HTML4), but many (if not most) browsers just allows
attributes without qoutes.

As long as user don't have other mistakes, it's not a security issue. It's
not vulnerable by itself, but it may be possible do some bad thing on some
implementations. It's just a precaution. It's good precaution as it does
not break any existing browsers. IMHO.

Regards,

--
Yasuo Ohgaki
yohgaki@ohgaki.net

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