oss-security - [CVE-2016-6316] Possible XSS Vulnerability in Action View

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Message-ID: <20160811175209.GA39068@TC.local>
Date: Thu, 11 Aug 2016 10:52:10 -0700
From: Aaron Patterson <tenderlove@...y-lang.org>
To: security@...e.de, rubyonrails-security@...glegroups.com,
	oss-security@...ts.openwall.com, ruby-security-ann@...glegroups.com
Subject: [CVE-2016-6316] Possible XSS Vulnerability in Action View

# Possible XSS Vulnerability in Action View

There is a possible XSS vulnerability in Action View.  Text declared as "HTML
safe" will not have quotes escaped when used as attribute values in tag
helpers.  This vulnerability has been assigned the CVE identifier
CVE-2016-6316.

Versions Affected:  >= 3.0.0.
Not affected:       < 3.0.0
Fixed Versions:     5.0.0.1, 4.2.7.1, 3.2.22.3

Impact
------
Text declared as "HTML safe" when passed as an attribute value to a tag helper
will not have quotes escaped which can lead to an XSS attack.  Impacted code
looks something like this:

```
content_tag(:div, "hi", title: user_input.html_safe)
```

Some helpers like the `sanitize` helper will automatically mark strings as
"HTML safe", so impacted code could also look something like this:

```
content_tag(:div, "hi", title: sanitize(user_input))
```

All users running an affected release should either upgrade or use one of the
workarounds immediately.

Releases
--------
The FIXED releases are available at the normal locations.

Workarounds
-----------
You can work around this issue by either *not* marking arbitrary user input as
safe, or by manually escaping quotes like this:

```
def escape_quotes(value)
  value.gsub(/"/, '&quot;'.freeze)
end

content_tag(:div, "hi", title: escape_quotes(sanitize(user_input)))
```

Patches
-------
To aid users who aren't able to upgrade immediately we have provided patches for
the two supported release series. They are in git-am format and consist of a
single changeset.

* 3-2-attribute-xss.patch - Patch for 3.2 series
* 4-2-attribute-xss.patch - Patch for 4.2 series
* 5-0-attribute-xss.patch - Patch for 5.0 series

Please note that only the 5.0.x and 4.2.x series are supported at present. Users
of earlier unsupported releases are advised to upgrade as soon as possible as we
cannot guarantee the continued availability of security fixes for unsupported
releases.

Credits
-------

Thanks to Andrew Carpenter of Critical Juncture for reporting this issue and
sending a patch to fix it!

-- 
Aaron Patterson
http://tenderlovemaking.com/

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View attachment "4-2-attribute-xss.patch" of type "text/plain" (2244 bytes)

View attachment "5-0-attribute-xss.patch" of type "text/plain" (2591 bytes)

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