[RavSinghChandan]

The numbering extra drops the space between the caption text and the number:

>>> markdown2.markdown("[#tablecounter Table @mytable: some interesting stuff]", extras=["numbering"])
'<figcaption class="tablecounter" id="counter-ref-mytable">Table1: some interesting stuff</figcaption>\n'

The wiki page shows Table 1: some interesting stuff for this input. The space was lost in #387 (Regex DOS fixes), which removed the \s* around the text before @ from the regex and added .strip(), so the trailing space went too. The text before @ is now followed by a space when there is one, so [#c @x: caption] still gives 1: caption.

The numbering test case didn't catch this because numbering.text was a copy of the expected HTML, so it never used the extra's syntax. It now has the [#counter text @id ...] definitions and [@id] references that produce numbering.html, which is unchanged; it fails on master.

Added a line to CHANGES.md (I used #770 for the number; I'll correct it if the PR gets another one)