Canonical informed users on Friday that the Ubuntu Forums website was breached after a hacker exploited a known vulnerability in one of the add-ons installed on the vBulletin-powered site.
Jane Silber, chief executive officer at Canonical, said in a security notice that the company learned about the breach on July 14, after someone claimed to have a copy of the Ubuntu Forums database.
An investigation revealed that the attacker exploited a known SQL injection vulnerability in Forum Runner, an add-on that allows users to access various types of forums from a native app installed on their mobile phone.
The hacker leveraged the flaw to access the forum’s “user” table, which stores usernames, email addresses and IPs for the site’s more than 2 million registered users. Silber pointed out that the attacker had not gained access to valid passwords.
“No active passwords were accessed; the passwords stored in [the user] table were random strings as the Ubuntu Forums rely on Ubuntu Single Sign On for logins,” Silber said. “The attacker did download these random strings (which were hashed and salted).”
The company is confident that the hacker did not access other Canonical or Ubuntu services, code repositories, or front-end servers. Canonical also believes the attacker was not able to do anything else than read information from the database.
Canonical says it has patched the vulnerability exploited by the attacker and updated its vBulletin installation to ensure that it’s at the latest patch level. The servers hosting the forum have been wiped clean and rebuilt, and all system and database passwords have been reset.
In order to prevent such breaches in the future, Canonical has installed the ModSecurity web application firewall (WAF) and it has taken steps to ensure that vBulletin component vulnerabilities are patched faster.
This was not the first time the Ubuntu Forums got hacked. In 2013, an attacker accessed email addresses and MD5-hashed passwords after hijacking a moderator’s account. Roughly 1.8 million users were affected at the time.
Earlier this year, a hacker breached the servers of the popular Linux Mint distribution and replaced legitimate download links with ones pointing to a backdoored version of the operating system.
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