An Internet bug had massive potential security implications. But good luck getting information on whether any actual damage was done.

A long-lasting bug called Heartbleed has undermined basic security across the Internet. In theory, it exposed encryption keys, users’ names, and passwords, and data for two-thirds of the world’s websites. This is because of a newly discovered flaw in software called OpenSSL, which is supposed to allow for encrypted data exchange (see “The Under-Funded Project Keeping the Web Secure”).