Disallowed Raw HTML (extension)
GFM enables the
tagfilter extension, where the following HTML tags will be filtered when rendering HTML output:
Filtering is done by replacing the leading
< with the entity
<. These tags are chosen in particular as they change how HTML is interpreted in a way unique to them (i.e. nested HTML is interpreted differently), and this is usually undesireable in the context of other rendered Markdown content.
All other HTML tags are left untouched.