Both of them. They could be done in the following combination: post a small paper on your website about the flaw, with all the details - but make sure it is pur

Both of them. They could be done in the following combination: post a small paper on your website about the flaw, with all the details - but make sure it is purely objective. Then e-mail the author, and send him the link to your article. Provided that he's (or she) a nice guy/gal, it shouldn't be much of a problem and you might even get some public credit by his/her part.