wp_mail incorrectly parses multiline From header

[arty.name]

wp_mail tries to parse From: header when it is contained in headers. It fails when the header is multiline. Multiline headers are common when non-ascii characters are used and quoted-printable escaping kicks in.

Example input:

From: =?UTF-8?Q?=D0=92=D0=B7=D0=B3=D0=BB=D1=8F=D0=B4=20=D0=BD=D0=B0=20=D0=BE?=
 =?UTF-8?Q?=D0=BA=D1=80=D1=83=D0=B6=D0=B0=D1=8E=D1=89=D0=B8=D0=B9=20=D0=BC?=
 =?UTF-8?Q?=D0=B8=D1=80?= <live-positive@yandex.ru>

Parsed email in $from_email:

=?UTF-8?Q?=D0=92=D0=B7=D0=B3=D0=BB=D1=8F=D0=B4=20=D0=BD=D0=B0=20=D0=BE?=

[arty.name]

proposed fix

[arty.name]

I have attached a patch which might fix the problem by improving how wordpress parses headers. First of all, it treats multiline headers as one (continuation of header can be easily detected by first character being a whitespace). Second, if there's a mb_decode_mimeheader present, it is used to parse the $from_name.

[arty.name]

Any chance for this to get some attention?

[stephenharris]

Refreshed patch added, includes unit test.

[desrosj]

28473-2.diff​ needs to be refreshed.