Wikimedia Bugzilla is closed!

To reproduce, upload a file that does raise a warning and click "ignore and submit file anyway button"

In 1.16 hidden fields were unconditionally not prefixed with wp, whereas in 1.17 in certain cases they are, breaking backwards compatibility. It kinda sucks to break an interface after only a single release.

$form = new HTMLForm( array(
	'Text' => array(
		'type' => 'text',
		'default' => 'foo',
	),
	'TextOverridden' => array(
		'type' => 'text',
		'name' => 'DifferentTextOverridden',
		'default' => 'foo',
	),
	'ArrayName' => array(
		'type' => 'hidden',
		'default' => 'foo',
	),
	'ArrayNameOverridden' => array(
		'type' => 'hidden',
		'name' => 'DifferentArrayNameOverridden',
		'default' => 'bar',
	),
) );
$form->addHiddenField( 'FunctionName','baz' );
$form->setTitle($this->getTitle());
$form->displayForm('');

=== 1.16.1 ===

<input name="wpText">
<input name="wpTextOverridden">
<input type="hidden" name="FunctionName">
<input type="hidden" name="ArrayName">
<input type="hidden" name="ArrayNameOverridden">

=== trunk ===

<input name="wpText">
<input name="DifferentTextOverridden">
<input type="hidden" name="FunctionName">
<input type="hidden" name="wpArrayName">
<input type="hidden" name="DifferentArrayNameOverridden">

The main change in 1.17 was to introduce the 'name' override: if you specified 'name' => 'Foo' in the descriptor array, that would be used unconditionally, and without any modification.  That applies to all types of fields.  Given that, there's no reason to special-case hidden fields *except* for B/C.  And as I said on IRC, I'd rather have it consistent and transiently incompatible, than inconsistent forever.

Specific issue raised was fixed in r79758.