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?
♥̧̧̧̛̣̘̟̘̥͓̫̪̹̪̪̮̯̞̘̙̦̝̭̭͕̜̰̩̗̟̹͔̜̥̟̗̗̥̦̠̖̫͕̺̻̞̥̹͇̱̥̥̻͇̦̙̣͊͗̉̽̈́̉͑̀́̃͒̏͋̃̅̇̊̏̎̈́͊͐̉͑̄̌̉́̈́́́̅̇͌̽̽͗́̄̾̓̈́̇̅͛́̈́͐̽̔̌̋̌̾́̿͌̔͊͆̈́̉́̎̔̊͗̊̂̎̍̏̈̀̏͋͌̋̽̄̐̽͐̀͘̕̕͘̕̚̚̚͘͜͜͜͠͝͠͝͠͝
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:
"\u2665\u034a\u0360\u0357"