email: add a blurb

Author: beledouxdenis

Misc/NEWS.d/next/Security/2026-01-16-14-40-31.gh-issue-143935.U2YtKl.rst

@@ -0,0 +1,6 @@
+Fixed a bug in the folding of comments when flattening an email message
+using a modern email policy. Comments consisting of a very long sequence of
+non-foldable characters could trigger a forced line wrap that omitted the
+required leading space on the continuation line, causing the remainder of
+the comment to be interpreted as a new header field. This enabled header
+injection with carefully crafted inputs.