I have an integration between Slack and my custom app via Slack Outgoing Webhook. Recently, I found that if a Slack message contains a URI (and this URI was recognized as URI in Slack) the JSON sent to my webhook has this link surrounded by corner brackets ('<' and '>').
So, for now, I've got two questions:
Is this intended behavior or a bug?
Is there any way to disable it?
Unfortunately, official Slack documentation is not very helpful.
This is the intended behavior. I don't think there is a way to disable it.
The behavior you noted above, happens when a Slack message has some formatted text in it. Not only for URIs but for other strings like channels, usernames, groups as well you will encounter these brackets. You'll need to write your code in order to parse these strings.
The good news is that these are well-defined strings, and they always follow a special structure. You can consult Slack documentation here, to know more about it.
Detect all sub-strings matching <(.*?)>
Within those sub-strings, format content starting with #C as a channel link
Format content starting with #U or #W as a user mention
Format content starting with !subteam as a user group mention
Format content starting with ! according to the rules for special mentions
For any other content within those sub-strings, format as a URL link
Once the format has been determined, check for a pipe (|) - if present, use the text following the pipe as the label for the link or
mention.
Markdown syntax for a link is pretty simple:
[Example](http://example.com/)
produces:
Example
But what if the link itself contains a closing bracket?
[Syntax](http://en.wikipedia.org/wiki/Syntax_(programming_languages))
produces:
Syntax)
which is obviously broken.
Edit
Putting the url in quotes does not work
Sometimes you need to encode ) with %29.
[Syntax](http://en.wikipedia.org/wiki/Syntax_(programming_languages%29)
E.g.: This was the only method I could find to get a correct Markdown preview in the Atom Editor.
You can try to escape the character:
[Syntax](http://en.wikipedia.org/wiki/Syntax_\(programming_languages\))
You can also encode the characters
[Syntax](http://en.wikipedia.org/wiki/Syntax_%28programming_languages%29)
The most reliable way I've found to do this is to use reference-style links instead of inline links.
Here is the wikipedia article on [Syntax][1]
[1]: http://en.wikipedia.org/wiki/Syntax_(programming_languages)
renders correctly as
Here is the wikipedia article on Syntax
I've found that with some sites, percent-escaping the parentheses will break URLs, especially anchors. For example, at least in my version of Firefox, this Android documentation link doesn't take me directly to the method with percent encoding.
But this one with a reference-style link does.
For example, at least in my version of Firefox, this Android documentation link
doesn't take me directly to the method [with percent encoding](https://developer.android.com/reference/android/webkit/WebView.html#addJavascriptInterface%28java.lang.Object,%20java.lang.String%29).
But this one with a [reference-style link][2] does.
I have found that using < around > the url seems to solve the problem.
In the two internal systems we use that use markdown.
Your mileage may vary with other systems.
[Test](<https://en.wikipedia.org/wiki/Slowloris_(computer_security)>)
Test
Quoting w3Schools:
URLs can only be sent over the Internet using the ASCII character-set.
So, you need to encode any special characters that is not a ASCII character into its respective ASCII character.
In your case, the characters for brackets or parenthesis are
open bracket ( - %28
closing bracket ) - %29
You can use this website to get the encoded url of any website link.
You don't have to scape it at all.
On GitHub, I've just done the following without any problems:
[Slowloris](https://en.wikipedia.org/wiki/Slowloris_(computer_security))
Actually, even here you can use it directly, as you can see here.
I am using Topsy, It returns me title of highest ranking article of my mebsite, It returns me one RSS file which contains post title with there link. For now i am only taking post name and using post title am trying to search in mysql database using following function like this:
get_post_by_title($postTitle,'post');
But the problem is topsy returns me post title but it also add some special characters in RSS file like " ' " replace with " ’ " this charecters.Because of this get_post_by_title() function does not return me post by title name.
EDIT : It returns me one post title like this :
iPad Applications In Bloom’s Taxonomy NEXT
Here single quote is special charecter.
Please help me. Thanks
First let's clear up a misconception: that character in your example is not a "special" character. It is Unicode code point U+2019, "RIGHT SINGLE QUOTATION MARK." Its HTML entity reference is ’. It's an ordinary character - it just happens to be an ordinary character that has no representation in ASCII. Before getting to an answer to your specific question, I need to tell you to read Joel Spolsky's article "The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets (No Excuses!)" - it is just what it says on the tin, and unless you absorb at least a little more knowledge about Unicode, you will keep running into problems like this. Don't fret too much: everyone runs into problems like this until they learn how to deal with text. Unicode isn't "hard" so much as it is "prone to exposing unconscious assumptions we make about how text works." †
Now, to your question.
If I'm reading you right, what's happening to you is that you have posts with non-ASCII characters in their titles such as ’ which aren't showing up when you search for them with get_post_by_title() (it seems like you're using something similar to the accepted answer on this question - is that right?) There are two paths to a solution: store the titles in a format that's easier for you to search, or use a searching method that can find non-ASCII characters.
Storing the titles differently would require that you run them through PHP's built-in htmlentities() function or before storing them in your Wordpress DB - you would also want to make sure that you convert characters with no HTML entity equivalent to '\xNN' form, and to make sure that your DB's collation/charset is set to UTF-8 or another Unicode-aware encoding. This will be a nontrivial amount of effort. ‡
Using a different searching method doesn't require tinkering with your DB or digging into WordPress internals, but it does require very careful fiddling with search string. You'll need to either use the exact character you're looking for in a search, expressed as a '\xNN' character reference if necessary, or use wildcards carefully in the search.
Either way, good luck. It may be possible to offer more specific advice if more of your code is visible.
†: By the way, your life with regards to Unicode will also get much, much easier if you use better languages than PHP and better databases than MySQL. WordPress is inextricably tied to PHP and MySQL: PHP & MySQL are both woefully, horrendous, hilariously bad at handling Unicode issues correctly. Your life as a programmer will get better if you extirpate PHP & MySQL from it.
‡: Seriously, PHP is atrociously bad at this, and MySQL is in a shoelaces-tied-together state of fumbling. Avoid them.
remove from wp-config.php
//define('DB_CHARSET', 'utf8');
//define('DB_COLLATE','utf8_unicode_ci');
You can easily remove special characters using preg_replace, see this post -> http://code-tricks.com/filter-non-ascii-characters-using-php/
I'm having the strangest issue with codeigniter. I have a site that has a search feature which displays the person's query in the url so that they can save the url. I make sure that the query text has gone through rawurlencode before I stick it in the url. However, Codeigniter still shoots me to an error page when there's a character in the query that isn't in my permitted_uri_characters configuration.
So even though my browser says /search-results/query/%22samplequery%22, I’m still getting the error about using non-permitted characters.
Is this a bug? I don’t have non-permitted characters in my url. I have a % sign and some numbers (which are all specifically permitted). It’s definitely the permitted_uri_characters setting that’s giving me grief. If I add a quotation mark to it, it allows the %22 query through no problem.
And to be clear, the query is coming from a form as post data, then being encoded in my controller and then redirected to a new page. There’s no way that the permitted_uri_characters is somehow being applied BEFORE it gets encoded.
This is driving me batty, as my only solution at the moment is to open up my permitted_uri_charcters to everything under the sun, which isn't very secure!
Seems like you'd need to add # to the permitted_uri_chars, even if you urlencode the email before sending it to site_url(). Might urldecode it before watching up the characters ...
Percent Symbol in CodeIgniter URI
Here is a post more specific to your problem.
http://sholsinger.com/archive/2009/04/passing-email-addresses-in-urls-with-codeigniter/
I tried with the permitted_uri_chars, and finally ended up passing the email as a query string (?email=bla#bla.com), not even urlencoding it. Works great :)
Could it be URL encoding the %20 to a " before codeigniter verify' it? How about adding that to the permitted char's list.
I have my own solution for this, it's messy and not optimal, but it works. You can create a table where you store (search_string , url_title).
Every time you perform a search, save the string, generate an url_title() and save it to the database. This way, you can redirect your user to a safe url, without missing the initial search.
I know somebody is gonna yell at me for this solution. But, if your site is small, and your traffic keeps low, it's a valid solution.
I'm using an '&' symbol with HTML5 and UTF-8 in my site's <title>. Google shows the ampersand fine on its SERPs, as do all the browsers in their titles.
http://validator.w3.org is giving me this:
& did not start a character reference. (& probably should have been escaped as &.)
Do I really need to do &?
I'm not fussed about my pages validating for the sake of validating, but I'm curious to hear people's opinions on this and if it's important and why.
Yes. Just as the error said, in HTML, attributes are #PCDATA meaning they're parsed. This means you can use character entities in the attributes. Using & by itself is wrong and if not for lenient browsers and the fact that this is HTML not XHTML, would break the parsing. Just escape it as & and everything would be fine.
HTML5 allows you to leave it unescaped, but only when the data that follows does not look like a valid character reference. However, it's better just to escape all instances of this symbol than worry about which ones should be and which ones don't need to be.
Keep this point in mind; if you're not escaping & to &, it's bad enough for data that you create (where the code could very well be invalid), you might also not be escaping tag delimiters, which is a huge problem for user-submitted data, which could very well lead to HTML and script injection, cookie stealing and other exploits.
Please just escape your code. It will save you a lot of trouble in the future.
Validation aside, the fact remains that encoding certain characters is important to an HTML document so that it can render properly and safely as a web page.
Encoding & as & under all circumstances, for me, is an easier rule to live by, reducing the likelihood of errors and failures.
Compare the following: which is easier? Which is easier to bugger up?
Methodology 1
Write some content which includes ampersand characters.
Encode them all.
Methodology 2
(with a grain of salt, please ;) )
Write some content which includes ampersand characters.
On a case-by-case basis, look at each ampersand. Determine if:
It is isolated, and as such unambiguously an ampersand. eg. volt & amp > In that case don't bother encoding it.
It is not isolated, but you feel it is nonetheless unambiguous, as the resulting entity does not exist and will never exist since the entity list could never evolve. E.g., amp&volt >. In that case, don't bother encoding it.
It is not isolated, and ambiguous. E.g., volt& > Encode it.
??
HTML5 rules are different from HTML4. It's not required in HTML5 - unless the ampersand looks like it starts a parameter name. "©=2" is still a problem, for example, since © is the copyright symbol.
However it seems to me that it's harder work to decide to encode or not to encode depending on the following text. So the easiest path is probably to encode all the time.
I think this has turned into more of a question of "why follow the spec when browser's don't care." Here is my generalized answer:
Standards are not a "present" thing. They are a "future" thing. If we, as developers, follow web standards, then browser vendors are more likely to correctly implement those standards, and we move closer to a completely interoperable web, where CSS hacks, feature detection, and browser detection are not necessary. Where we don't have to figure out why our layouts break in a particular browser, or how to work around that.
Specifically, if HTML5 does not require using & in your specific situation, and you're using an HTML5 doctype (and also expecting your users to be using HTML5-compliant browsers), then there is no reason to do it.
Well, if it comes from user input then absolutely yes, for obvious reasons. Think if this very website didn't do it: the title of this question would show up as Do I really need to encode ‘&’ as ‘&’?
If it's just something like echo '<title>Dolce & Gabbana</title>'; then strictly speaking you don't have to. It would be better, but if you don't, no user will notice the difference.
Could you show us what your title actually is? When I submit
<!DOCTYPE html>
<html>
<title>Dolce & Gabbana</title>
<body>
<p>Am I allowed loose & mpersands?</p>
</body>
</html>
to http://validator.w3.org/ - explicitly asking it to use the experimental HTML 5 mode - it has no complaints about the &s...
In HTML, a & marks the begin of a reference, either of a character reference or of an entity reference. From that point on, the parser expects either a # denoting a character reference, or an entity name denoting an entity reference, both followed by a ;. That’s the normal behavior.
But if the reference name or just the reference opening & is followed by a white space or other delimiters like ", ', <, >, &, the ending ; and even a reference to represent a plain, & can be omitted:
<p title="&">foo & bar</p>
<p title="&">foo & bar</p>
<p title="&">foo & bar</p>
Only in these cases can the ending ; or even the reference itself be omitted (at least in HTML 4). I think HTML 5 requires the ending ;.
But the specification recommends to always use a reference like the character reference & or the entity reference & to avoid confusion:
Authors should use "&" (ASCII decimal 38) instead of "&" to avoid confusion with the beginning of a character reference (entity reference open delimiter). Authors should also use "&" in attribute values since character references are allowed within CDATA attribute values.
Update (March 2020): The W3C validator no longer complains about escaping URLs.
I was checking why image URLs need escaping and hence tried it in https://validator.w3.org. The explanation is pretty nice. It highlights that even URLs need to be escaped. [PS: I guess it will be unescaped when it's consumed since URLs need &. Can anyone clarify?]
<img alt="" src="foo?bar=qut&qux=fop" />
An entity reference was found in the document, but there is no
reference by that name defined. Often this is caused by misspelling
the reference name, unencoded ampersands, or by leaving off the
trailing semicolon (;). The most common cause of this error is
unencoded ampersands in URLs as described by the WDG in "Ampersands in
URLs". Entity references start with an ampersand (&) and end with a
semicolon (;). If you want to use a literal ampersand in your document
you must encode it as "&" (even inside URLs!). Be careful to end
entity references with a semicolon or your entity reference may get
interpreted in connection with the following text. Also keep in mind
that named entity references are case-sensitive; &Aelig; and æ
are different characters. If this error appears in some markup
generated by PHP's session handling code, this article has
explanations and solutions to your problem.
It depends on the likelihood of a semicolon ending up near your &, causing it to display something quite different.
For example, when dealing with input from users (say, if you include the user-provided subject of a forum post in your title tags), you never know where they might be putting random semicolons, and it might randomly display strange entities. So always escape in that situation.
For your own static HTML content, sure, you could skip it, but it's so trivial to include proper escaping, that there's no good reason to avoid it.
If the user passes it to you, or it will wind up in a URL, you need to escape it.
If it appears in static text on a page? All browsers will get this one right either way, and you don't worry much about it, since it will work.
Yes, you should try to serve valid code if possible.
Most browsers will silently correct this error, but there is a problem with relying on the error handling in the browsers. There is no standard for how to handle incorrect code, so it's up to each browser vendor to try to figure out what to do with each error, and the results may vary.
Some examples where browsers are likely to react differently is if you put elements inside a table but outside the table cells, or if you nest links inside each other.
For your specific example it's not likely to cause any problems, but error correction in the browser might for example cause the browser to change from standards compliant mode into quirks mode, which could make your layout break down completely.
So, you should correct errors like this in the code, if not for anything else so to keep the error list in the validator short, so that you can spot more serious problems.
A couple of years ago, we got a report that one of our web apps wasn't displaying correctly in Firefox. It turned out that the page contained a tag that looked like
<div style="..." ... style="...">
When faced with a repeated style attribute, Internet Explorer combines both of the styles, while Firefox only uses one of them, hence the different behavior. I changed the tag to
<div style="...; ..." ...>
and sure enough, it fixed the problem! The moral of the story is that browsers have more consistent handling of valid HTML than of invalid HTML. So, fix your damn markup already! (Or use HTML Tidy to fix it.)
If & is used in HTML then you should escape it.
If & is used in JavaScript strings, e.g., an alert('This & that'); or document.href, you don't need to use it.
If you're using document.write then you should use it, e.g. document.write(<p>this & that</p>).
If you're really talking about the static text
<title>Foo & Bar</title>
stored in some file on the hard disk and served directly by a server, then yes: it probably doesn't need to be escaped.
However, since there is very little HTML content nowadays that's completely static, I'll add the following disclaimer that assumes that the HTML content is generated from some other source (database content, user input, web service call result, legacy API result, ...):
If you don't escape a simple &, then chances are you also don't escape a & or a or <b> or <script src="http://attacker.com/evil.js"> or any other invalid text. That would mean that you are at best displaying your content wrongly and more likely are suspectible to XSS attacks.
In other words: when you're already checking and escaping the other more problematic cases, then there's almost no reason to leave the not-totally-broken-but-still-somewhat-fishy standalone-& unescaped.
The link has a fairly good example of when and why you may need to escape & to &
https://jsfiddle.net/vh2h7usk/1/
Interestingly, I had to escape the character in order to represent it properly in my answer here. If I were to use the built-in code sample option (from the answer panel), I can just type in & and it appears as it should. But if I were to manually use the <code></code> element, then I have to escape in order to represent it correctly :)