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From "Duncan Jones (JIRA)" <>
Subject [jira] [Commented] (LANG-1042) StringEscapeUtils.escapeHtml() does not escape single quote
Date Wed, 08 Oct 2014 12:35:39 GMT


Duncan Jones commented on LANG-1042:

It's not really clear from the Javadocs what these methods are supposed to achieve. Clearly
you were expecting the methods to render safe any user input that might be directly injected
into other pieces of HTML. Looking at the code, it seems they only replace named entities
(for XML this includes escaping {{'}} to {{&amp;apos;}}). At the very least, we should
improve the Javadocs to make it clearer what is being escaped. 

If our goal is to sanitise user input, then we should consider whether escaping single quotes
is the only change to make. Any such change would break compatibility with earlier versions,
so I'm not sure we could address this before 4.0 (unless we are convinced it's a bug, which
is hard to prove since the docs are so vague).

> StringEscapeUtils.escapeHtml() does not escape single quote
> -----------------------------------------------------------
>                 Key: LANG-1042
>                 URL:
>             Project: Commons Lang
>          Issue Type: Bug
>            Reporter: Robert Sussland
>            Priority: Critical
> The String Escape Utils should ensure that encoded data cannot escape from a string.
However in HTML (starting with 1.0 and until the present), attribute values may be denoted
by either single or double quotes. Therefore single quotes need to be escaped just as much
as double quotes. 
> From the standard:
> {quote}
> By default, SGML requires that all attribute values be delimited using either double
quotation marks (ASCII decimal 34) or single quotation marks (ASCII decimal 39). Single quote
marks can be included within the attribute value when the value is delimited by double quote
marks, and vice versa. Authors may also use numeric character references to represent double
quotes (&amp;#34\;) and single quotes (&amp;#39\;). For double quotes authors can
also use the character entity reference &amp;quot;.
> {quote}
> Note that there have been several bugs in the wild in which string encoders use this
library under the hood, and as a result fail to properly escape html attributes in which user
input is stored:
> <div title='<%=user_data%>'>Howdy</div>
> if user_data = ' onclick='payload' ' 
> then an attacker can inject their code into the page even if the developer is using the
string escape utils to escape the user string.

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