Weird (unicode?) characters

unicode special-characters zalgo
user1960364 picture user1960364 · Mar 6, 2014 · Viewed 11.6k times · Source

A user has been posting some weird characters on my site and I'd like to block them from doing so but without blocking characters used in foreign languages... Therefore, using a regex such as [a-z0-9!@#$%^&*()...] isn't an option.

Could someone explain to me what is happening here, a break down of why it displays the way it does. How the characters are created and how can I prevent them from doing it? 




♥̧̧̧̛̣̘̟̘̥͓̫̪̹̪̪̮̯̞̘̙̦̝̭̭͕̜̰̩̗̟̹͔̜̥̟̗̗̥̦̠̖̫͕̺̻̞̥̹͇̱̥̥̻͇̦̙̣͊͗̉̽̈́̉͑̀́̃͒̏͋̃̅̇̊̏̎̈́͊͐̉͑̄̌̉́̈́́́̅̇͌̽̽͗́̄̾̓̈́̇̅͛́̈́͐̽̔̌̋̌̾́̿͌̔͊͆̈́̉́̎̔̊͗̊̂̎̍̏̈̀̏͋͌̋̽̄̐̽͐̀͘̕̕͘̕̚̚̚͘͜͜͜͠͝͠͝͠͝




Thanks

EDIT: So they're used to accent characters? Is there a common practice or way to prevent users from exploiting them without blocking them completely? I don't know enough about foreign languages or their actual use/purpose so crafting something to limit the use of the combining characters is outside my scope of possibilities. :-/

Answer

McDowell picture McDowell · Mar 6, 2014

These are combining diacritical marks. For the character é e-acute you can represent it using either the code point U+00E9 (LATIN_SMALL_LETTER_E_WITH_ACUTE) or the sequence U+0065 U+0301 (LATIN_SMALL_LETTER_E COMBINING_ACUTE_ACENT) where the text renderer places the accent above the preceding code point.

The user is exploiting this with a sequence of combining marks:

codepoint   glyph   escaped    UTF-8           info
=======================================================================
U+2665      ♥       \u2665     e2,99,a5,       MISCELLANEOUS_SYMBOLS, OTHER_SYMBOL
U+034a      ͊       \u034a     cd,8a,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0360      ͠       \u0360     cd,a0,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0357      ͗       \u0357     cd,97,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0309      ̉       \u0309     cc,89,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+033d      ̽       \u033d     cc,bd,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0344      ̈́       \u0344     cd,84,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0309      ̉       \u0309     cc,89,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0351      ͑       \u0351     cd,91,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0340      ̀       \u0340     cd,80,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+035d      ͝       \u035d     cd,9d,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0301      ́       \u0301     cc,81,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0303      ̃       \u0303     cc,83,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0352      ͒       \u0352     cd,92,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+030f      ̏       \u030f     cc,8f,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+034b      ͋       \u034b     cd,8b,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0303      ̃       \u0303     cc,83,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0305      ̅       \u0305     cc,85,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0307      ̇       \u0307     cc,87,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+030a      ̊       \u030a     cc,8a,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+030f      ̏       \u030f     cc,8f,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+030e      ̎       \u030e     cc,8e,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0344      ̈́       \u0344     cd,84,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+034a      ͊       \u034a     cd,8a,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0350      ͐       \u0350     cd,90,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0309      ̉       \u0309     cc,89,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0351      ͑       \u0351     cd,91,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0304      ̄       \u0304     cc,84,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+030c      ̌       \u030c     cc,8c,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0309      ̉       \u0309     cc,89,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0301      ́       \u0301     cc,81,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0344      ̈́       \u0344     cd,84,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0341      ́       \u0341     cd,81,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0301      ́       \u0301     cc,81,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0305      ̅       \u0305     cc,85,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0307      ̇       \u0307     cc,87,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+034c      ͌       \u034c     cd,8c,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+033d      ̽       \u033d     cc,bd,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+033d      ̽       \u033d     cc,bd,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0357      ͗       \u0357     cd,97,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0301      ́       \u0301     cc,81,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0360      ͠       \u0360     cd,a0,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0304      ̄       \u0304     cc,84,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+033e      ̾       \u033e     cc,be,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0343      ̓       \u0343     cd,83,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0344      ̈́       \u0344     cd,84,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0307      ̇       \u0307     cc,87,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0358      ͘       \u0358     cd,98,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0305      ̅       \u0305     cc,85,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+035d      ͝       \u035d     cd,9d,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+035b      ͛       \u035b     cd,9b,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0301      ́       \u0301     cc,81,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0344      ̈́       \u0344     cd,84,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0350      ͐       \u0350     cd,90,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+033d      ̽       \u033d     cc,bd,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0314      ̔       \u0314     cc,94,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+030c      ̌       \u030c     cc,8c,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+030b      ̋       \u030b     cc,8b,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+030c      ̌       \u030c     cc,8c,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+033e      ̾       \u033e     cc,be,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0360      ͠       \u0360     cd,a0,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0301      ́       \u0301     cc,81,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+033f      ̿       \u033f     cc,bf,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+034c      ͌       \u034c     cd,8c,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0314      ̔       \u0314     cc,94,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0315      ̕       \u0315     cc,95,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+034a      ͊       \u034a     cd,8a,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0346      ͆       \u0346     cd,86,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0344      ̈́       \u0344     cd,84,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0309      ̉       \u0309     cc,89,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+035d      ͝       \u035d     cd,9d,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0341      ́       \u0341     cd,81,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0315      ̕       \u0315     cc,95,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+030e      ̎       \u030e     cc,8e,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0314      ̔       \u0314     cc,94,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+030a      ̊       \u030a     cc,8a,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0357      ͗       \u0357     cd,97,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0358      ͘       \u0358     cd,98,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+030a      ̊       \u030a     cc,8a,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0315      ̕       \u0315     cc,95,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0302      ̂       \u0302     cc,82,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+030e      ̎       \u030e     cc,8e,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+030d      ̍       \u030d     cc,8d,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+030f      ̏       \u030f     cc,8f,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0308      ̈       \u0308     cc,88,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0340      ̀       \u0340     cd,80,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+030f      ̏       \u030f     cc,8f,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+031a      ̚       \u031a     cc,9a,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+034b      ͋       \u034b     cd,8b,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+031a      ̚       \u031a     cc,9a,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+031a      ̚       \u031a     cc,9a,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+034c      ͌       \u034c     cd,8c,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+030b      ̋       \u030b     cc,8b,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+033d      ̽       \u033d     cc,bd,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0304      ̄       \u0304     cc,84,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0310      ̐       \u0310     cc,90,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+033d      ̽       \u033d     cc,bd,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0350      ͐       \u0350     cd,90,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+031b      ̛       \u031b     cc,9b,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0358      ͘       \u0358     cd,98,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0300      ̀       \u0300     cc,80,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0323      ̣       \u0323     cc,a3,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0318      ̘       \u0318     cc,98,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+031f      ̟       \u031f     cc,9f,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+035c      ͜       \u035c     cd,9c,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0318      ̘       \u0318     cc,98,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+035c      ͜       \u035c     cd,9c,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0325      ̥       \u0325     cc,a5,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0353      ͓       \u0353     cd,93,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+032b      ̫       \u032b     cc,ab,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+032a      ̪       \u032a     cc,aa,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0339      ̹       \u0339     cc,b9,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+032a      ̪       \u032a     cc,aa,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+032a      ̪       \u032a     cc,aa,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+035c      ͜       \u035c     cd,9c,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+032e      ̮       \u032e     cc,ae,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+032f      ̯       \u032f     cc,af,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0327      ̧       \u0327     cc,a7,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+031e      ̞       \u031e     cc,9e,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0318      ̘       \u0318     cc,98,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0319      ̙       \u0319     cc,99,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0326      ̦       \u0326     cc,a6,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+031d      ̝       \u031d     cc,9d,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+032d      ̭       \u032d     cc,ad,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+032d      ̭       \u032d     cc,ad,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0355      ͕       \u0355     cd,95,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+031c      ̜       \u031c     cc,9c,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0330      ̰       \u0330     cc,b0,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0329      ̩       \u0329     cc,a9,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0317      ̗       \u0317     cc,97,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+031f      ̟       \u031f     cc,9f,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0339      ̹       \u0339     cc,b9,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0354      ͔       \u0354     cd,94,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+031c      ̜       \u031c     cc,9c,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0325      ̥       \u0325     cc,a5,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+031f      ̟       \u031f     cc,9f,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0317      ̗       \u0317     cc,97,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0317      ̗       \u0317     cc,97,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0325      ̥       \u0325     cc,a5,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0326      ̦       \u0326     cc,a6,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0320      ̠       \u0320     cc,a0,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0316      ̖       \u0316     cc,96,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+032b      ̫       \u032b     cc,ab,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0355      ͕       \u0355     cd,95,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+033a      ̺       \u033a     cc,ba,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0327      ̧       \u0327     cc,a7,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+033b      ̻       \u033b     cc,bb,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+031e      ̞       \u031e     cc,9e,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0325      ̥       \u0325     cc,a5,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0327      ̧       \u0327     cc,a7,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0339      ̹       \u0339     cc,b9,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0347      ͇       \u0347     cd,87,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0331      ̱       \u0331     cc,b1,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0325      ̥       \u0325     cc,a5,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0325      ̥       \u0325     cc,a5,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+033b      ̻       \u033b     cc,bb,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0347      ͇       \u0347     cd,87,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0326      ̦       \u0326     cc,a6,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0319      ̙       \u0319     cc,99,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK
U+0323      ̣       \u0323     cc,a3,          COMBINING_DIACRITICAL_MARKS, NON_SPACING_MARK

Some points I made in the comments:

  • The Unicode standard considers all sequences of code points to be valid if not meaningful (see chapter 2 of Unicode 6)
  • Unicode does not describe how code points should be displayed - that's up to the text rendering technology
  • Normalizing to NFC and matching on code point category are likely to be useful for detecting redundant diacritics
  • You can create sequences like the one above using browser consoles

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