After nearly a month of debate, Google Chrome developers have decided that a potential security flaw that can be exploited to spoof the URL displayed in the web browser’s address bar is worth fixing.
The issue was discovered in early June by David Leo, a researcher at UK-based security firm Deusen. A proof-of-concept (PoC) released by the company shows arbitrary content as being hosted on oracle.com. Other experts noticed that the bug can also be exploited to spoof HTTPS websites.
“When Google Chrome loads a new page, the content of the old page will remain for a while (and there is a way to keep it this way),” Leo told SecurityWeek.
Google was informed of this issue on June 7, but the search giant initially said it was not a security problem because users cannot interact with the spoofed content.
Chrome developers said the bug is a “render denial-of-service” and noted that it will likely not be fixed because it cannot be exploited for phishing attacks. However, Leo and others have pointed out that the bug still represents a potential security vulnerability.
For example, any domain can be made to look like it belongs to a business accredited by the BBB. Furthermore, pranksters can leverage the bug to make the official domain of the White House display a message that reads “We love Islamic State,” Leo said. Others have pointed out that malicious actors could make a reputable domain display a message instructing visitors to call a certain phone number.
Another possibility, suggested by IT security consultant Sijmen Ruwhof, is to create a regular phishing page that allows user interaction and make it exploit the spoofing bug to temporarily display the targeted website’s official domain. After a few seconds, the original phishing page can be loaded again, allowing cybercriminals to harvest the user’s data.
“After two seconds the impersonification process is stopped, enough time for a user to validate the URL bar and identity of the web site and start filling in forms,” Ruwhof noted.
At the beginning of July, Chrome developers picked up the discussion and agreed that it represents a potential security flaw.
“Lack of interaction does not completely mitigate it. Lots of phishing attacks these days tell you to call a phone number. No interactions,” one developer noted.
Charlie Reis, a Google software engineer working on the Chrome web browser, said on Tuesday that the issue is worth fixing, “even if the attack is not as severe as a general URL spoof where the page is responsive to user input.”
Some users have also reported being able to reproduce the address spoofing flaw on certain versions of Firefox and Opera.
The bug seems to have been around for several years. A researcher reported finding the same issue back in 2012, but since he didn’t manage to make the spoofed page responsive, it remained unfixed.
This is not the first web browser security issue identified by Leo. Earlier this year, the expert reported uncovering a universal cross-site scripting (UXSS) vulnerability in Internet Explorer, and an address bar spoofing flaw in Safari.
