There are several security issues affecting all major Web browsers that have remained unaddressed for years (probably because the bad guys haven’t leveraged them aggressively enough, but the potential is there). The problem is that the only known ways to fix these issues (adequately) is to “break the Web” — i.e. negatively impact the usability of a significant and unacceptable percentage of websites

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The Web won’t be safe, let alone secure, unless we break it