Protect against browser extension injected Javascript code
Being able to disable someone's browser extension usually implies taking over the browser. I don't think it's possible. It would be a huge security risk. Your purpose maybe legit, but consider the scenario of webmasters programatically disabling addblockers for users in order to get them to view the advertisments.
In the end it's the user's responsability to make sure they have a clean OS when making online banking transactions. It's not the website's fault that the user is compromised
UPDATE We should wrap things up. Something like:
<meta name="disable-extension-feature" content="read-dom" />
or
<script type="text/javascript">
Browser.MakeExtension.MallwareLogger.to.not.read.that.user.types(true);
</script>
doesn't exist and i'm sure there won't be implemented in the near future. Use any means necessary to best use the current up to date existing technologies and design your app as best as you can security wise. Don't waste your energy trying to cover for users who souldn't be making payments over the internet in the first place
UPDATE (2019-10-16): This isn't a "real" solution - meaning you should not rely on this as a security policy. Truth is, there is no "real" solution because malicious addons can hijack/spoof JavaScript in a way which in not detectable. The technique below was more of an exercise for me to figure out how to prevent simple key logging. You could expand on this technique to make it more difficult for hackers... but Vlad Balmos said it best in his answer below - Don't waste your energy trying to cover for users who souldn't be making payments over the internet in the first place.
You can get around the key logging by using a javascript prompt. I wrote a little test case (which ended up getting a little out of hand). This test case does the following:
- Uses a prompt() to ask for the credit card number on focus.
- Provides a failsafe when users check "prevent additional dialogs" or if the user is somehow able to type in the CC field
- Periodically checks to make sure event handlers haven't been removed or spoofed and rebinds/ warns the user when necessary.
http://jsfiddle.net/ryanwheale/wQTtf/
prompt('Please enter your credit card number');
Tested in IE7+, Chrome, FF 3.6+, Android 2.3.5, iPad 2 (iOS 6.0)
Your question is interesting, and thoughtful (+1'd), however unfortunately the proposed security does not provide real security, thus no browser will ever implement it.
One of the core principle on browser/web/network security is to resist from the desire of implementing a bogus security feature. Web will be less secure with the feature than without!
Hear me out:
Everything execute on the client-side can be manipulated. Browsers are just another HTTP clients that talks to server; server should never ever trust the computation result, or checks done in front-end Javascript. If someone can simply bypass your "security" check code executed in a browser with a extension, they can surely fire the HTTP request directly to your server with curl to do that. At least, in a browser, skilled users can turn to Firebug or Web Inspector and bypass your script, just like what you do when you debug your website.
The <meta> tag stopping extensions from injection does make the website more robust, but not more secure. There are a thousand ways to write robust JavaScript than praying for not having an evil extension. Hide your global functions/objects being one of them, and perform environment sanity check being another. GMail checks for Firebug, for example. Many websites detects Ad block.
The <meta> tag does make sense in terms of privacy (again, not security). There should be a way to tell the browser that the information currently present in the DOM is sensitive (e.g. my bank balance) and should not be exposed to third parties. Yet, if an user uses OS from vender A, browser from vender B, extension from vender C without reading through it's source code to know exactly what they do, the user have already stated his trust to these venders. Your website will not be at fault here. Users who really cares about privacy will turn to their trusted OS and browser, and use another profile or private mode of the browser to check their sensitive information.
Conclusion: If you do all the input checks on sever-side (again), your website is secure enough that no <meta> tag can make it more secure. Well done!