HTML 5 Cheat Sheet

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Browser Securability Chart

There are a few sites charting browser capabilities as they related to the HTML 5 / CSS 3 standard. I have not seen any that mention security. There may not be a need for it, but e.g. 'sandbox' will be ignored in down browsers, but which HTML 5 compliant browsers support it. If there are differences in implementations, my assumption is that there will be differences in security configuration / settings.

Cross Origin Request

Input Validation

Local Storage (a.k.a. Offline Storage, Web Storage)




Use the "sandbox" attribute for untrusted content (iFrame)


Content Deliverability

CDN or src links to foreign domains = know your content

Progressive Enhancements and Graceful Degradation Risks

The best practice now is to determine the capabilities that a browser supports and augment with some type of substitute for capabilities that are not directly supported. This may mean an onion-like element, e.g. falling through to a Flash Player if the <video> tag is unsupported, or it may mean additional scripting code from various sources that should be code reviewed.


I haven't seen any specific to CSS 3 and it's been a while since I worried about url / !import. I think privacy leaks are the most well know - e.g. querying global history using :visited (

Javascript and Javascript Frameworks

Do we have cheatsheets for Javascript (e.g. use closures, protect the global namespace) or any of the frameworks like JQuery,, Prototype, Mootools

Related Cheat Sheets

OWASP Cheat Sheets Project Homepage

Developer Cheat Sheets (Builder)

Assessment Cheat Sheets (Breaker)

Mobile Cheat Sheets

OpSec Cheat Sheets (Defender)

Draft Cheat Sheets

Authors and Primary Editors