Jonathan Mayer, a lawyer and computer scientist at Stanford University, was getting ready to teach his first Coursera course last week when he discovered large security problems on the provider of massive open online courses. As he described on his blog, Mayer found that, among other things, any instructor could "dump the entire user database, including over 9 million names and email addresses" and that "if you are logged into your Coursera account, any website that you visit can list your course enrollments." Coursera has acknowledged the problems and said that it has fixed them. Mayer's blog says that the MOOC provider has made some but not all of the fixes.