After reading the input using NekoHTML antisamy builds a DOM tree out of it then validates all of its nodes with the given policy file.ĪntiSamy provides the following boilerplate policy files that you can use (can be downloaded from OWASP project page) and further can be modified to meet your project requirements. NekoHTML adds missing parent elements automatically closes elements with optional end tags and can handle mismatched inline element tags. The parser can scan HTML files and "fix up" many common mistakes that human (and computer) authors make in writing HTML documents. Also, it provides user friendly error messages to lĮt the user know what HTML, validation or security errors existed.ĪntiSamy uses NekoHTML and the given policy file for validating the given HTML/CSS input markup. NekoHTML is a simple HTML scanner and tag balancer that enables application programmers to parse HTML documents and access the information using standard XML interfaces. AntiSamy follows the whitelist approach to get the clean HTML/CSS output markup. AntiSamy is an OWASP Open source API that will allow user submitted HTML/CSS and limits the potential malicious content to get through. AntiSamy is one such framework which can sanitize/validate the given input markup which can contain HTML, CSS according to a given policy file. But the problem with XSD schema validation is it provides no response or error message to the user and XSD needs to be created for all HTML elements.ĪntiSamy solves the problem of allowing HTML content and also protecting the application from possible attacks like XSS. It provides a flexible implementation, whitelisting of tags. Convert all the given HTML input to XML and then verify the xml using the XSD schema file. One last option could be to devise an XSD schema file by defining list of allowed html tags and attributes. These parsers can effectively whitelist the allowed formatting tag but using this we can not leverage HTML and forces user to learn new language. These markup parsers converts these set of tags to equivalent HTML. One can use markup parsers such as BBCode and WikiText which provides alternate set of markup tags similar to HTML. There by not encoding/escaping the unverified input definitely opens up new possibilities for XSS. Forums & blogs are places where content posted from one user will be displayed back to other website users. In that instance encoding/escaping cannot performed on the posted HTML markup as the input needs to be rendered in the browser. In many websites where application developers wishes to provide an option of posting HTML markup so that users can post formatted and interactive data.
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