Atlassian patches One-Click flaw that allowed hackers to steal user sessions

Atlassian logo on a computer screen

Security researchers have warned of a critical flaw in the Atlassian project and software development platform that hackers can use to take over an account and control some of the apps connected through its single sign-on (SSO) capability.

According to Check Point Research (CPR), hackers could exploit the flaw to access Atlassian’s Jira, a bug-tracking and agile project-management tool used by over 65,000 customers, including Cisco, Pfizer, and Visa.

The flaw focuses on Atlassian’s use of SSO to ensure continuous navigation between subdomains for related products, such as Jira ( and Confluence ( This creates a potential attack scenario involving injecting malicious code into the platform, then leveraging a session fixation flaw to hijack a valid user session and take control of an account.

Researchers proved that account takeover was possible on Atlassian accounts accessible by subdomains under

To exploit the flaw, hackers would have to lure a victim into clicking on a crafted link coming from the “Atlassian” domain via social media, a fake email, or a messaging app, etc. By clicking on the link, the payload would send a request on the victim’s behalf to the Atlassian platform, which would perform the attack and steal the user session. Then the hacker logs onto the victim's Atlassian apps associated with the account, gaining all the sensitive information stored there.

“What makes a supply chain attack such as this one so significant is the fact that once the attacker leverages these vulnerabilities and takes over an account, he can plant backdoors that he can use in the future for his attack. This can create severe damage which will be identified and controlled only much after the damage is done,” said researchers.

Lewis Jones, threat intelligence analyst at Talion, told ITPro that successfully exploiting these flaws could result in a supply-chain attack whereby an attacker can take over an account, use it to perform unauthorized actions, such as edit Confluence pages, access Jira tickets, and even inject malicious implants to stage further attacks down the line.


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“Furthermore, if an attacker gains access to a Jira account, the attacker can proceed to gain control of a Bitbucket account which could lead to an attacker being able to pilfer credentials. This could grant them permissions to access or alter source code, make the repository public, or even insert backdoors,” he said.

“Whilst details have recently emerged, a fix for the flaw was released in May. Users are advised to ensure that updates are implemented as soon as possible, and to continue monitoring for any further developments."

CPR disclosed its research findings to Atlassian on January 8, and Atlassian deployed a fix on May 18.

Rene Millman

Rene Millman is a freelance writer and broadcaster who covers cybersecurity, AI, IoT, and the cloud. He also works as a contributing analyst at GigaOm and has previously worked as an analyst for Gartner covering the infrastructure market. He has made numerous television appearances to give his views and expertise on technology trends and companies that affect and shape our lives. You can follow Rene Millman on Twitter.