How do I properly encode a mailto link?

asp.net html xss urlencode mailto

10,719

You are putting some content in a URL, then representing that URL in HTML. So URLEncode it then HTMLEncode what you get from URLEncode.

10,719

Scott Stafford

I want what everybody wants. A job where I can change the world modestly for the better, that makes me enough money so I can have everything I want and not so much that my kids want to kill me for the inheritance, and that gives me enough fame to stroke my ego yet I can still dine out in peace.

Updated on June 04, 2022

Comments

Scott Stafford almost 2 years
I am generating some HTML and I want to generate an XSS- and database-content-safe mailto link. What is the proper encoding to use here? How's this?
```
myLiteral.Text = string.Format(
  "mailto:{0}?Content-Type=text/html&amp;Subject={1}&amp;body={2}", 
  HttpUtility.UrlEncode(email_address),
  HttpUtility.UrlEncode(subject),
  HttpUtility.UrlEncode(body_message));
```
Should I use UrlEncode here? HtmlEncode? Do what I did, then HtmlEncode the entirety? I'm writing HTML of a URL, so I'm a little unclear...

@Quentin, is this what you're describing? (Changed &s to & since I'm about to HtmlEncode...)
```
myLiteral.Text = 
  HttpUtility.HtmlEncode(HttpUtility.UrlEncode(
    string.Format(
      "mailto:{0}?Content-Type=text/html&Subject={1}&body={2}", 
      email_address, subject, body_message)));
```
- Scott Stafford over 12 years
  
  @liho1eye: I think that's only true for an ASP Literal if myLiteral.Mode == Encode, which is not the default. But the second version should have the effect you were going for, yes?
Scott Stafford over 12 years

I tried.. is the 2nd version of the code in my question what you had in mind?
Erlend over 12 years

I would go with the first one. Or a mix of the two. Htmlattributeencoding the whole value, and url encoding the values inserted into the url
Quentin almost 10 years

@Yuck — It is really an answer. The second sentence describes exactly what needs to be done.
Quentin almost 10 years

@ScottStafford — Just seen the comment (2.5 years later), "yes".