Security Experts:

Flaw in Fortinet Login Page Allowed Attackers to Phish Credentials

A reflected cross-site scripting (XSS) vulnerability in a login page used to access some Fortinet product services could have been exploited for highly efficient phishing attacks, a researcher reported on Friday.

The flaw, discovered by Synetis security consultant Yann Cam, is related to the single sign-on (SSO) login page used by Fortinet customers to gain access to certain protected resources.

The France-based researcher discovered that the page, hosted at, was plagued by an XSS vulnerability that could have allowed a malicious actor to inject malicious code and take control of the page simply by getting the targeted user to click on a specially crafted link.

An attacker could have exploited the security hole to load a remote JavaScript file designed to harvest the victim’s credentials and send them to a server before the login process was completed.

If the value of the vulnerable parameter is changed, users get an error when trying to log in to their account. However, the XSS flaw also allowed the attacker to manipulate the appearance of the login page and hide this error message.

Many users could have fallen victim to attacks leveraging this flaw because the phishing page was actually the legitimate login page, hosted on an HTTPS domain, and the only difference from a normal login would have been a one-second delay in the authentication process.

The expert noted that a malicious hacker could have leveraged the vulnerability in phishing and spear-phishing campaigns aimed at system administrators. A video published by the researcher shows how easy it would have been for an attacker to harvest credentials.

Cam reported the flaw to Fortinet on November 6, 2015, and it was patched by the vendor roughly three weeks later. The details of the vulnerability were only disclosed now because the researcher discovered a second reflected XSS while taking a satisfaction survey related to the first vulnerability. He waited until Fortinet patched this issue as well before making his findings public.

This is not the only Fortinet product vulnerability whose details were disclosed this year. In mid-January, the company confirmed the existence of an SSH backdoor in the FortiOS operating system. Further analysis conducted by the vendor revealed that the backdoor was also present in FortiSwitch switches, FortiAnalyzer centralized log and reporting appliances, and FortiCache web caching appliances.

Related: Critical Flaw in FireEye Appliances Exploitable by Sending an Email

Related: Palo Alto Networks Fixes PAN-OS Vulnerabilities

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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.