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Stack Exchange suffers from some zero-width space characters being inserted in the post data quite infrequently when the text "values " (with a trailing space) is being used.

For people not too familiar with invisible unicode characters, you may copy-paste the content from the below examples to an online editor like the green textarea from https://r12a.github.io/app-conversion/ and tap Convert, then you'll discover the hidden single or double spaces ​/\u{200B}/U+200B that were inserted.

Now, this bug doesn't happen all the time... from my analysis, it happens maybe 1 time out of 500 usages of text "values ". But with the amount of posts on the Stack Exchange network, I was easily able to find with SEDE thousands of occurrences of this issue across Stack Exchange.

Demonstration that the bug, when it kicks in, affects both the title and the body of the post:

Demonstration that it also affects Mathematics (and not just Stack Overflow):

Demonstration that to trigger the bug, the pattern doesn't require a space before "values " (but requires one after):

Demonstration that it doesn't affect all posts, by comparing some recent posts created on the same day (Oct 26, 2018):

Potentially oldest Stack Overflow post affected:

Which could mean that the bug wasn't there in 2008/2009/2010.

  • You apparently have used SEDE to identify these posts. Any reason for not sharing your SEDE query but just linking to the SEDE home page? – Erik A Nov 7 '18 at 18:29
  • @ErikvonAsmuth because I used an old query that wasn't targetting this specific issue at all: I just happened to figure out after many months using it that there was an abnormal frequency of the word "values": data.stackexchange.com/stackoverflow/query/712284/unicode-title – Cœur Nov 7 '18 at 18:35
  • I just hope this doesn't qualify as a pluralization bug... – Cœur Nov 7 '18 at 18:37
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    You would almost expect it to be related to the client used, either a certain webbrowser or maybe one the apps, although the latter seems unlikely given the elaborate questions that expose said bug. – rene Nov 8 '18 at 8:42

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