Weird (unicode?) characters
Solution 1
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
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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
- Just type in a UTF-16 JavaScript string literal like
"\u2665\u034a\u0360\u0357"
- You can just use the code point value from the charts for anything in the basic multilingual plane
- For anything outside the BMP you'll have to translate the code points to UTF-16
- Just type in a UTF-16 JavaScript string literal like
Solution 2
Blocking these codepoints may be enough for you:
http://en.wikipedia.org/wiki/Combining_character#Unicode_ranges
Related videos on Youtube
user1960364
Updated on September 15, 2022Comments
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user1960364 over 1 year
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?
♥̧̧̧̛̣̘̟̘̥͓̫̪̹̪̪̮̯̞̘̙̦̝̭̭͕̜̰̩̗̟̹͔̜̥̟̗̗̥̦̠̖̫͕̺̻̞̥̹͇̱̥̥̻͇̦̙̣͊͗̉̽̈́̉͑̀́̃͒̏͋̃̅̇̊̏̎̈́͊͐̉͑̄̌̉́̈́́́̅̇͌̽̽͗́̄̾̓̈́̇̅͛́̈́͐̽̔̌̋̌̾́̿͌̔͊͆̈́̉́̎̔̊͗̊̂̎̍̏̈̀̏͋͌̋̽̄̐̽͐̀͘̕̕͘̕̚̚̚͘͜͜͜͠͝͠͝͠͝
ThanksEDIT: 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. :-/
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Remy Lebeau about 10 yearsHow are you allowing users to post text to your site in the first place??
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kirilloid about 10 yearsThey are called "combining [diacritic] characters". You could search for codepoints range.
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user1960364 about 10 yearsI've already taken the standard security measures to prevent XSS and SQL Injectons, is there something else I should be worried about?
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user1960364 about 10 yearsWould you happen to know what character requires the most of these combining characters and how many characters it consists of?
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McDowell about 10 yearsCan't help you there. The Unicode standard considers all sequences valid if not linguistically meaningful. Visual appearance of any code point is outside the scope of the standard - that is, it's the problem of whatever draws the text.
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McDowell about 10 yearsYou can generate them easily in a browser console using UTF-16 escape sequences like
"\u2665\u034a\u0360\u0357"
assuming font support. Anything in the basic multilingual plane you can just use the code point value from the charts. You should look at normalization to NFC and the character categories which you can match on in many regex implementations. -
kirilloid about 10 yearsInformation (links) in this comment is worth adding to the answer itself. It is much more useful, than characters table.
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RemcoGerlich about 10 yearsHow on earth do you get from "users can post arbitrary Unicode strings" to "users can probably do a lot more damage"? It's just a Unicode string that looks odd.
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vonbrand about 10 years@RemcoGerlich, if "weird characters" get through, and OP is worried about cleaning by eliminating many characters like <>&....