Zendesk said three of its clients were affected by the breach: Twitter, Tumblr and Pinterest. Zendesk announced the breach via a blog posting, while Tumblr has notified its affected users via email. Twitter and Pinterest are expected to notify their affected users as well. According to Zendesk's blog post, it found the breach this week and was able to patch the vulnerability and close the hacker's access. Zendesk said it believes the hacker downloaded email addresses of users that had contacted those three Web sites for support and also obtained the e-mail subject lines of those support emails. No passwords, password hashes or encrypted passwords are believed to have been stolen, and no user accounts are believed to have been compromised. The chatter on Main Street (a.k.a. Google, Yahoo! and other search sites) is always of interest to investors on Wall Street. Thus, each day, TheStreet compiles the stories that are trending on the Web, and highlights the news that could make stocks move.-- Written by Brittany Umar.