I guess this is related to https://phabricator.wikimedia.org/T180857
There are 2 issues when generating a new secure HTML code via Special:SecureHTML.
- When calling Special:SecureHTML this warning appears:
Notice: Undefined index: in /mediawiki/extensions/SecureHTML/SpecialSecureHTML.php on line 40
- After entering a HTML code the Secure HTML code is parsed and shown. However there is a warning:
Strict Standards: call_user_func() expects parameter 1 to be a valid callback, non-static method SpecialSecureHTML::trySubmit() should not be called statically in /mediawiki/includesformForm.php on line 613
Tried both the REL_1_27 and master version of https://www.mediawiki.org/wiki/Extension:Secure_HTML and MediaWiki 1.27.4.