控制变量法找了一下原因，不是Firefox和迷雾通的问题，是ubock origin这个扩展所导致的。我Google了一下“ublock origin dns leak”证实了这个推论。
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具体来说是”将代理域名映射至真实域名”这个选项导致的
禁用就好了
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firefox浏览器， tor浏览器才是最安全的。
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请问怎么设置？可以详细说说吗？谢谢。
仅针对于Windows10上的Firefox 90版本（其他情况我不了解）。如果你发现dns泄露，并安装有ublock origin这个扩展，那么是ublock origin的内置功能“将代理域名映射至真实域名”导致的（ubo会默认启用这个功能），要关闭它请点击浏览器右上方的ublock origin图标，再点击三个齿轮的图标，在管理界面最左一栏有个设置，将其中的“将代理域名映射至真实域名”取消勾选即可。
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迷雾通当tor浏览器的前置代理，tor是firefox的一个分支浏览器
可是，沒有看到“将代理域名映射至真实域名”的选框 
猜测是“uncloak cname...”那个选项。但是印象中这个dns leak的bug很久以前就被修复了.我用最新版1.37.2配vmess没有遇到此问题。
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谢谢。 ::
非常感谢 这帮助我解决了一个隐患
ublock的解释
From uBO 1.34.0 and above. Before 1.34.0, this was an advanced setting since 1.25.0.
Enable/disable the uncloaking of canonical names -- enabled by default.
For background information see "What's CNAME of your game? This DNS-based tracking defies your browser privacy defenses".
The setting will be disabled on platforms not supporting this feature. It's currently supported only on Firefox.
In some edge cases, it might be necessary to disable this setting to prevent network-related issues. For example, "Pages load slowly when uBlock Origin is installed", which occurred when funneling network requests through a proxy.
Important note when using extension-based proxy service: Extension-based proxy services are often done on-the-fly through a browser API, and in such case uBO's own DNS queries to uncloak canonical names will NOT be caught and proxied by an extension-based proxy service. So you may want to disable this setting when using an extension-based proxy service.
我近期在一个网站遇到界面语言突然变成了中文，然而我全程挂梯、Accept-Language 里根本没有 zh*
不能排除 DNS 泄漏的可能
可能是utc+8导致的？