Security Experts:

Mozilla Patches Critical Code Execution Flaw in Firefox

An update released this week by Mozilla for Firefox 58 patches a critical vulnerability that can be exploited by a remote attacker for arbitrary code execution.

Mozilla developer Johann Hofmann discovered that arbitrary code execution is possible due to unsanitized output in the browser UI.

The vulnerability, tracked as CVE-2018-5124, affects Firefox versions 56 through 58 and it has been fixed with the release of Firefox 58.0.1. According to Mozilla, Firefox for Android and Firefox 52 ESR are not impacted. Linux distributions have also started pushing out updated packages that include the fix.

“The vulnerability is due to insufficient sanitization of HTML fragments in chrome-privileged documents by the affected software,” Cisco said in an advisory describing this flaw. “An attacker could exploit the vulnerability by persuading a user to access a link or file that submits malicious input to the affected software. A successful exploit could allow the attacker to execute arbitrary code with the privileges of the user. If the user has elevated privileges, the attacker could compromise the system completely.”

Firefox 58, which Mozilla released on January 23, patches more than 30 vulnerabilities, including a potentially exploitable use-after-free bug and various memory safety issues that have been rated critical.

Firefox 58 also addresses over a dozen high severity flaws, including use-after-free, buffer overflow, and integer overflow bugs. A vulnerability that allows WebExtensions to bypass user prompts to download and open an arbitrarily file has also been classified as high severity.

Ten of these security holes were also addressed earlier this month in the Thunderbird email client with the release of version 52.6. Mozilla pointed out that the flaws typically cannot be exploited against Thunderbird using specially crafted emails.

Mozilla runs a bug bounty program for Firefox and the organization claims it has paid out nearly $1 million to experts who reported vulnerabilities. Hackers can earn between $3,000 and $7,500 for critical and high severity flaws in Mozilla software, but a novel exploit or form of exploitation can earn more than $10,000.

In addition to its software bug bounty program, Mozilla rewards flaws discovered in its websites and services with up to $5,000. The organization says it has paid out a total of roughly $3 million across its bug bounty programs.

Related: Mozilla Conducts Security Audit of Firefox Accounts

Related: Firefox to Block Canvas-based Browser Fingerprinting

Related: Firefox 57 to Get New XSS Protections

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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.