Why is "®" being rendered as "®" without the bounding semicolon
I've been running into a problem that was revealed through our Google adwords-driven marketing campaign. One of the standard parameters used is "region". When a user searches and clicks on a sponsored link, Google generates a long URL to track the click and sends a bunch of stuff along in the referrer. We capture this for our records, and we've noticed that the "Region" parameter is coming through incorrectly. What should be
http://ravercats.com/meow?foo=bar®ion=catnip
is instead coming through as:
http://ravercats.com/meow?foo=bar®ion=catnip
I've verified that this occurs in all browsers. It's my understanding that HTML entity syntax is defined as follows:
&VALUE;
where the leading boundary is the ampersand and the closing boundary is the semicolon. Seems straightforward enough. The problem is that this isn't being respected for the ® entity, and it's wreaking all kinds of havoc throughout our system.
Does anyone know why this is occurring? Is it a bug in the DTD? (I'm looking for the current HTML DTD to see if I can make sense of it) I'm trying to figure out what would be common across browsers to make this happen, thus my looking for the DTD.
Here is a proof you can use. Take this code, make an HTML file out of it and render it in a browser:
<html>
<a href="http://foo.com/bar?foo=bar®ion=US®ister=lowpass®_test=fail&trademark=correct">http://foo.com/bar?foo=bar®ion=US®ister=lowpass®_test=fail&trademark=correct</a>
</html>
EDIT: To everyone who's suggesting that I need to escape the entire URL, the example URLs above are exactly that, examples. The real URL is coming directly from Google and I have no control over how it is constructed. These suggestions, while valid, don't answer the question: "Why is this happening".
Answer
Although valid character references always have a semicolon at the end, some invalid named character references without a semicolon are, for backward compatibility reasons, recognised by modern browsers' HTML parsers.
Either you know what that entire list is, or you follow the HTML5 rules for when & is valid without being escaped (e,g, when followed by a space) or otherwise always escape & as & whenever in doubt.
For reference, the full list of named character references that are recognised without a semicolon is:
AElig, AMP, Aacute, Acirc, Agrave, Aring, Atilde, Auml, COPY, Ccedil, ETH, Eacute, Ecirc, Egrave, Euml, GT, Iacute, Icirc, Igrave, Iuml, LT, Ntilde, Oacute, Ocirc, Ograve, Oslash, Otilde, Ouml, QUOT, REG, THORN, Uacute, Ucirc, Ugrave, Uuml, Yacute, aacute, acirc, acute, aelig, agrave, amp, aring, atilde, auml, brvbar, ccedil, cedil, cent, copy, curren, deg, divide, eacute, ecirc, egrave, eth, euml, frac12, frac14, frac34, gt, iacute, icirc, iexcl, igrave, iquest, iuml, laquo, lt, macr, micro, middot, nbsp, not, ntilde, oacute, ocirc, ograve, ordf, ordm, oslash, otilde, ouml, para, plusmn, pound, quot, raquo, reg, sect, shy, sup1, sup2, sup3, szlig, thorn, times, uacute, ucirc, ugrave, uml, uuml, yacute, yen, yuml
However, it should be noted that only when in an attribute value, named character references in the above list are not processed as such by conforming HTML5 parsers if the next character is a = or a alphanumeric ASCII character.
For the full list of named character references with or without ending semicolons, see here