This vulnerability is app specific and does not pertain to all environments. If you have a specific question or need assistance with this issue, please open a Support Ticket.
Issue
XSS vulnerability in sanitize_css in Action Pack
There is an XSS vulnerability in the `sanitize_css` method in Action Pack. This vulnerability has been assigned the CVE identifier CVE-2013-1855.
Versions Affected: All.
Not affected: None.
Fixed Versions: 3.2.13, 3.1.12, 2.3.18
Impact
Carefully crafted text can bypass the sanitization provided in the `sanitize_css` method in Action Pack. Impacted code will look like this:
sanitize_css(some_user_input)
All users running an affected release should either upgrade or use one of the work arounds immediately.
Releases
The 3.2.13 and 3.1.12 releases are available at the normal locations.
Workarounds
To work around this issue, you can apply the following monkey patch:
```
module HTML
class WhiteListSanitizer
# Sanitizes a block of css code. Used by #sanitize when it comes across a style attribute
def sanitize_css(style)
# disallow urls
style = style.to_s.gsub(/url\s*\(\s*[^\s)]+?\s*\)\s*/, ' ')
# gauntlet
if style !~ /\A([:,;#%.\sa-zA-Z0-9!]|\w-\w|\'[\s\w]+\'|\"[\s\w]+\"|\([\d,\s]+\))*\z/ ||
style !~ /\A(\s*[-\w]+\s*:\s*[^:;]*(;|$)\s*)*\z/
return ''
end
clean = []
style.scan(/([-\w]+)\s*:\s*([^:;]*)/) do |prop,val|
if allowed_css_properties.include?(prop.downcase)
clean << prop + ': ' + val + ';'
elsif shorthand_css_properties.include?(prop.split('-')[0].downcase)
unless val.split().any? do |keyword|
!allowed_css_keywords.include?(keyword) &&
keyword !~ /\A(#[0-9a-f]+|rgb\(\d+%?,\d*%?,?\d*%?\)?|\d{0,2}\.?\d{0,2}(cm|em|ex|in|mm|pc|pt|px|%|,|\))?)\z/
end
clean << prop + ': ' + val + ';'
end
end
end
clean.join(' ')
end
end
end
```
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-css_sanitize.patch - Patch for 3.2 series
* 3-1-css_sanitize.patch - Patch for 3.1 series
* 3-0-css_sanitize.patch - Patch for 3.0 series
* 2-3-css_sanitize.patch - Patch for 2.3 series
Please note that only the 3.1.x and 3.2.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.
For a link to the above information and patches for download, please see the following Google Document: https://groups.google.com/forum/?fromgroups=#!topic/rubyonrails-security/4_QHo4BqnN8
March 20, 2013 5:21am PDT (12:22pm UTC) - While a minority of users are likely affected by this vulnerability, we recommend everyone upgrade.
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