is_email() does not recognize IDN domains

[OlegCorner]

Insufficient validation of the domain name in function is_email of wp-includes/formatting.php.
WordPress 3.5.1 > , including trunk.
Test for invalid characters does not test Unicode symbols in international domain, such as Cyrillic domains and other Unicode domains.

[SergeyBiryukov]

Related: #17491

[nacin]

Hi OlegCorner. We had quite a bit of "fun" with \P{L}, as it is possible to compile PCRE without Unicode support. See #22692. Not sure what to do here, though it does seem to be possible to check for this support with a separate check, then allow IDN domains through if so. Or, there might be another way to check for this.

[mitjajez]

Can't find how to make a patch here, but i belive we need do add idn_to_ascii function ​php > 5.4.0

$domain = idn_to_ascii($domain);

on line #2422 in wp-includes/formatting.php

and later

$email = implode( '@', array($local, $domain));

on line #2446 in wp-includes/formatting.php

[rmccue]

It's worth mentioning that WordPress now includes an IDN parser inside Requests: Requests_IDNAEncoder. We could convert IDN domains to their ASCII representation, and if that fails, the domain is invalid. If it succeeds, it can then go through the regular email checks.

[birgire]

#44616 was marked as a duplicate.