I recently upgraded my site from version 1.28.2 to 1.33.1. It was successful albeit with some minor issues. The main one being that the custom backgrounds I was using no longer appear to function. Basically, my site is divided into different groups of articles. These articles are marked by special templates that assign it a category and also use HTML tags to change the background and link colors. Below are some examples:
http://omniversenexus.net/wiki/Template:Galactic_Crucibles
http://omniversenexus.net/wiki/Template:Erudite_Tales
After upgrading, even though the link recolorings still work, the body tag does not, and thus, no background appears. But prior to the upgrade, these templates worked just fine.
Here's what I have in my LocalSettings.php in regards to the HTML Tags.
#HTML Tags
include_once "$IP/extensions/HTMLTags/HTMLTags.php";
$wgHTMLTagsAttributes['a'] = array( 'href', 'class', 'id' );
$wgHTMLTagsAttributes['body'] = array( 'style', 'background', 'bgcolor', 'class', 'id' );
$wgHTMLTagsAttributes['meta'] = array( 'itemprop', 'content' );
$wgHTMLTagsAttributes['span'] = array( 'itemprop', 'itemscope', 'itemtype' );
$wgHTMLTagsAttributes['img'] = array( 'style', 'src', 'height', 'width', 'alt', 'class', 'id' );
$wgHTMLTagsAttributes['style'] = array();
What do I need to change in order to get the backgrounds to reappear again? The only other change I had to make during the upgrade was to disable the HeaderTabs extension as otherwise, the site would throw a 500 error. Here is the version information on my wiki if it proves necessary:
http://omniversenexus.net/wiki/Special:Version
EDIT: In the process of upgrading, I also changed to PHP Version 7.3 from 5.6.