You need trust level 2 to post links to select websites and trust level 3 to post any link. To check your trust level, open your character profile page and add .json at the end, then search for every instance of trust_level. The highest level is your current standing.
https://www.curseforge.com/wow/addons/censusplusclassic
https://wowpop.appspot.com/
I can’t post either, but you can also use the option Performatted text to include the full links.
Edit: here are the requirements for every trust level: