Re: Strange Behavior by Win IE 6 displaying bad UTF-8

From: Tom Gewecke (
Date: Sun Apr 23 2006 - 13:09:04 CST

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    On Apr 23, 2006, at 9:49 AM, Richard Wordingham wrote:

    > It's actually very simple. Given an initial byte E1, the next two
    > bytes must be of the form 10xxxxxx 10xxxxxx. If the parser then
    > trusts alleged UTF-8 to be valid UTF-8 (which it should not), it can
    > then ignore the non-x bits. Now, it is the second and third bytes
    > that are incorrect, being FC and D0 rather than BC and 90, ie. bit 6
    > is 1 whereas it must be 0. The low six bits of FC (wrong) and BC
    > (correct) and D0 (wrong) and 90 (correct) are the same.

    Thanks! This would explain some other weird things I have seen in Win
    Outlook, where invalid byte sequences can get displayed as Chinese

    Apparently there is some code around which also generates erroneous
    UTF-8 like this, which is then pretty hard to detect for a Win IE user.

    Any security issues from this ability to read invalid UTF-8 as if it
    were valid?

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