Virtual Event Today: Supply Chain Security Summit - Register Now

Security Experts:

Connect with us

Hi, what are you looking for?



Tech Support Scammers Exploiting Unpatched Firefox Bug

Mozilla is working on addressing a Firefox bug that has been exploited by tech support scammers to lock the browser when users visit specially crafted websites.

Mozilla is working on addressing a Firefox bug that has been exploited by tech support scammers to lock the browser when users visit specially crafted websites.

Attacks were spotted recently by Jérôme Segura of Malwarebytes, who told SecurityWeek that there are currently two known Firefox bugs that have been abused in tech support scams.

Exploitation only requires that users visit the websites set up by the cybercrooks. These sites display warnings and instruct victims to call “Windows support” at a specified number.

Firefox tech support scam

Segura informed Mozilla of one bug, which has the bug ID 1438214, two years ago, when a very similar flaw had been exploited by scammers against Chrome users. The flaw allows an attacker to freeze the browser by exploiting the download blob API in a way that consumes all CPU resources.

The researcher recently decided to revisit this bug and discovered that it remains unfixed. He also identified a newer bug that has also been exploited by tech support scammers.

“The newer bug abuses notifications by perpetually asking users for the same authorization,” Segura told SecurityWeek, explaining that this flaw appears to be a variation of a previously fixed issue that involved authentication pop-ups and which had been exploited for years.

Based on information in the new bug report created by Segura, Mozilla has known about this issue for at least three months — Mozilla developers flagged Segura’s report as a duplicate — but a fix has yet to be released.

Mozilla has not responded to SecurityWeek’s request for comment, but based on discussions in the bug reports, a patch is expected to be included in Firefox 71, which is scheduled for release on December 3.

Until a patch becomes available, users who encounter the scam websites can forcefully close Firefox from the Task Manager on Windows or using the Force Quit option on macOS — the bug affects Firefox on both Windows and macOS.

Related: Vulnerability Patched in Firefox Password Manager

Related: Firefox Zero-Day Vulnerability Exploited in Targeted Attacks

Related: Mozilla Hardens Firefox Against Injection Attacks

Written By

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.

Click to comment

Daily Briefing Newsletter

Subscribe to the SecurityWeek Email Briefing to stay informed on the latest threats, trends, and technology, along with insightful columns from industry experts.

Join this webinar to learn best practices that organizations can use to improve both their resilience to new threats and their response times to incidents.


Join this live webinar as we explore the potential security threats that can arise when third parties are granted access to a sensitive data or systems.


Expert Insights

Related Content


Zendesk is informing customers about a data breach that started with an SMS phishing campaign targeting the company’s employees.


Less than a week after announcing that it would suspended service indefinitely due to a conflict with an (at the time) unnamed security researcher...


The release of OpenAI’s ChatGPT in late 2022 has demonstrated the potential of AI for both good and bad.


Satellite TV giant Dish Network confirmed that a recent outage was the result of a cyberattack and admitted that data was stolen.


The changing nature of what we still generally call ransomware will continue through 2023, driven by three primary conditions.

Application Security

PayPal is alerting roughly 35,000 individuals that their accounts have been targeted in a credential stuffing campaign.


No one combatting cybercrime knows everything, but everyone in the battle has some intelligence to contribute to the larger knowledge base.


A recently disclosed vBulletin vulnerability, which had a zero-day status for roughly two days last week, was exploited in a hacker attack targeting the...