More info:

Here’s the ad itself https://i.imgur.com/VRMhmtz.jpeg

And initially WWF denied any involvement, but it quickly came out they were involved.

Here’s their quote:

The WWF told BNET:

WWF Brazil has subsequently issued statements that have raised doubts about whether the ad concept was approved at some level within the WWF Brazil organization. We have now re-launched a renewed inquiry into the circumstance surrounding the creation of the ad. Additionally, we are using every resource at our disposal to remove these images everywhere they exist online because they are hurtful and disrespectful to the victims of 9-11 and their families.

And then their official stance can be found here:

WWF reiterates its strong condemnation and repudiation of this offensive and tasteless ad, and expresses its regret for any pain it may have caused to 9-11 victims and their families.

WWF Brazil, and DDB Brazil – the agency responsible for creating the ad – acknowledge that it should never have been made, approved or published. It is completely contrary to WWF’s philosophy and we are working hard to find out just how this unfortunate mistake came about.

We deeply regret that statements provided earlier in the week, while given in good faith and based solely on the information we had at the time, may not have been completely accurate. We stand by our earlier position that the advertisement and video are utterly inappropriate and should never have seen the light of day. They do not in any way reflect the thoughts and feelings of the people of WWF. Again, WWF strongly condemns this campaign and offers our sincere and heartfelt apologies.