Datum This object extracts aggregate types of data structures or arrays from a record in the file object.
We avoid buffer overflows and format string exploits remember those? To avoid SQL injectionwe never build database queries by concatenating user-supplied data. These measures protect the integrity of the data on our servers, but what about our non-malicious users?
These days, most new websites accept user input which will later be displayed to other users. Browsers are starting to offer some defense to these attacks, but historically the onus has been on web developers to ensure that we recognize where we are sending user input to the browser and that we properly escape that data.
Escaping user input Many developers have opinions on the proper place to escape user input. This highlights another weakness of this method: I prefer to maintain the data in its original form and handle it with care elsewhere.
On the backend For years, the languages commonly used for web development have included libraries that properly handle HTML escaping.
Good developers clearly indicate in the code and documentation where user-created data exists, and they use appropriate libraries to escape all such data as it is converted into an HTML page.
Barring problems in the library implementation or lapses in vigilance, this is a solid approach, and it allows a lot more flexibility than the previously-discussed method.
For example, it is now possible to echo the input as-is back to the creator for editing purposes.
The unsafe way document.
The safe way document. Sometimes we need to escape the string way before we add it to a DOM node. Enter various hacks to make that happen. Then it turns out that you sometimes need to escape part of an HTML tag attribute. You eventually settle on something like the following.
Your programming aesthetic takes over and one evening you convert it. You only traverse the string once. You handle escaping both within and outside of attributes.
Wow, you think, there must be a better way. And then you think back to "the safe way": We can take advantage of this to make string escaping fast, safe, and dead-simple.
Chapter 18 HTTP and Forms. Communication must be stateless in nature [ ] such that each request from client to server must contain all of the information necessary to understand the request, and cannot take advantage of any stored context on the server. In HTML, the ampersand character (“&”) declares the beginning of an entity reference (a special character).
If you want one to appear in text on a web page you should use the encoded named entity “ & ”—more technical mumbo-jumbo at srmvision.com 4 CHAPTER 1.
HTML Main Commands As described above an HTML program (also called an HTML script) is a sequence of three kinds of tokens ordinary text characters, tags, and special symbols.