Moodle Plugins directory: Plugin type: Filters | Moodle.org
Filters 
Filters operate on all the text content in Moodle (such as resources, forum posts, user profiles, glossary entries and so on). They can process the text to change formatting, change words, add links, embed media and so on.
Join the discussions about filters in the General add-ons forum, or for Mathematics filters, the Mathematics tools forum.