存储HTML时避免XSS攻击

Question

My site stores HTML that is generated by the user. Then of course this data is rendered on a web page. What are the best practices for rending the HTML and avoiding XSS attacks? Is stripping <script> and <iframe> tags enough? Will this cover all browsers? I heard of old browsers rendering HTML from weird encoding... how can I handle this?

I would like a general answer, not related to any languages or technologies.

Answer 1

You could use libraries like Jsoup especially their whitelist-sanitizer to prevent XSS.

In general, I think it is a better/safer aproach to use a white list , rather than filtering black listed tags. Besides, HTML should be avoided in the first place. Instead, some simple markup, like markdown , should be used.

Answer 2

I can assure you there is no way to safely do what you are asking. A crafty hacker will always be able to exploit a system that allows arbitrary html from the user, even when cleaned up by stripping away certain tags. This is exactly why tools like markdown and BBcode exist. Why look, even StackOverflow is using similar.

The road you are considering traveling down is littered with 10,000 exploited web sites.

Answer 3

You're lost when will allow your user do set HTML on your page, there a re wide range of possibilities like onmouseover"myEvilJS" or

Answer 4

Minimum you must convert this symbols.
& -> &
< -> &lt;
> -> &gt;
“ -> &quot;
' -> &#x27;
/ -> &#x2F;