An unpatched vulnerability affecting the RainLoop webmail client can be exploited to hijack a user’s session and steal their emails, according to application security firm Sonar.
RainLoop is an open source web-based email client used by many organizations. Sonar reported identifying thousands of internet-exposed instances using the Shodan search engine.
Sonar’s researchers discovered that RainLoop 1.16.0 — this is the latest version of the application and it was released roughly one year ago — is affected by a stored cross-site scripting (XSS) vulnerability that can be exploited against default configurations.
An attacker could exploit the flaw by simply sending a specially crafted email to a RainLoop user. Once the victim opens the malicious email, a hidden JavaScript payload is executed in the browser without other user interaction being required.
The security hole, tracked as CVE-2022-29360, is caused by what Sonar describes as a “logic bug after the sanitization process.” The company has made available technical details in a blog post published this week.
Sonar warned that an attacker could exploit the vulnerability to gain access to highly sensitive information that may be stored in the victim’s emails, including passwords, documents and password reset links. The company has released a video showing the exploit in action.
The vulnerability was initially reported to RainLoop developers in late November 2021 and there were two more responsible disclosure attempts in December and January, but Sonar said it received no response.
SecurityWeek has also reached out to RainLoop developers for comment and will update this article if they respond.
Sonar did develop an unofficial patch, but users are told to use it at their own risk. While RainLoop remains unpatched, Sonar noted that SnappyMail, a RainLoop fork, is actively maintained and is not affected by this vulnerability, which is why users have been advised to switch to SnappyMail.
Related: Malicious Emails Can Crash Cisco Email Security Appliances
Related: SonicWall Patches Y2K22 Bug in Email Security, Firewall Products
Related: ‘ProxyToken’ Exchange Server Vulnerability Leads to Email Compromise

Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.
More from Eduard Kovacs
- Waterfall Security, TXOne Networks Launch New OT Security Appliances
- Hitachi Energy Blames Data Breach on Zero-Day as Ransomware Gang Threatens Firm
- New York Man Arrested for Running BreachForums Cybercrime Website
- Exploitation of Recent Fortinet Zero-Day Linked to Chinese Cyberspies
- Mozilla Patches High-Severity Vulnerabilities With Release of Firefox 111
- Microsoft: 17 European Nations Targeted by Russia in 2023 as Espionage Ramping Up
- Cybercriminals, APT Exploited Telerik Vulnerability in Attacks on US Government Agency
- US Charges Two Men Over Use of Hacked Law Enforcement Database for Doxing
Latest News
- Millions Stolen in Hack at Cryptocurrency ATM Manufacturer General Bytes
- Waterfall Security, TXOne Networks Launch New OT Security Appliances
- Hitachi Energy Blames Data Breach on Zero-Day as Ransomware Gang Threatens Firm
- NBA Notifying Individuals of Data Breach at Mailing Services Provider
- Adobe Acrobat Sign Abused to Distribute Malware
- New York Man Arrested for Running BreachForums Cybercrime Website
- Huawei Has Replaced Thousands of US-Banned Parts With Chinese Versions: Founder
- Latitude Financial Services Data Breach Impacts 300,000 Customers
