Firefox 52 Brings WebAssembly and Security Fixes

Mozilla patches Firefox for 28 different vulnerabilities, with seven rated as having critical impact.


Mozilla released Firefox 52 on March 7, providing users of the open-source web browser with new features as well well as patches for 28 security vulnerabilities. The Firefox 52 release is the second major milestone release of Firefox in 2017 so far, following the Firefox 51 milestone that debuted on Jan. 24.

The biggest new feature in Firefox 52 is support for the WebAssembly standard, that multiple browser vendors including Apple and Microsoft have been working on since June 2015. The core promise of WebAssembly is that it will enable native code to run in a browser, providing the ability for more complex applications to run with greater levels of performance.

Firefox 52 now also provides an improved capability for WiFi users to log into captive portals at mobile hotspots. With a captive portal, users first need to login or agree to the terms of use, for a given access point, before being granted access.

"These captive portals are often problematic because the login page itself is hard to discover if the operating system doesn’t detect it," Nick Nguyen, VP of Firefox at Mozilla, wrote in a blog post. "With today's release, Firefox now automatically detects captive portals and notifies you about the need to log in."

Also of note in the Firefox 52 release is the fact that Mozilla is now officially disabling all plugins that use the Netscape Plugin API (NPAPI), other than Adobe Flash. Mozilla has been warning developers and users since Oct. 2015 that it was going to remove support for NPAPI.

From a security perspective, Firefox 52 provides a new security feature to help protect users against insecure cookies. The Strict Secure Cookies specification, which is now in Firefox 52, will prevent unencrypted HTTP sites from being able to set secure cookies. The basic idea behind the Strict Secure Cookies specification is to help make sure that security is maintained throughout the web transport process.

"In some cases, this will prevent an insecure site from setting a cookie with the same name as an existing "secure" cookie from the same base domain," Mozilla stated in the Firefox 52 release notes.


Mozilla is patching Firefox 52 for 28 different vulnerabilities, of which seven are rated as having critical impact. Two of the seven critical vulnerabilities (CVE-2017-5398 and CVE-2017-5399) are identified by Mozilla as being memory safety bugs.

Three of the critical flaws are Use-After-Free memory issues (CVE-2017-5402, CVE-2017-5403 and CVE-2017-5404). The other two critical flaws include an ASLR (Address Space Layout Randomization) bypass and a Memory Corruption issue when handling error results.

Among the flaws rated by Mozilla as having moderate impact is address bar spoofing issued that could have potentially been triggered via a simple drag-and-drop action.

"When dragging content from the primary browser pane to the address bar on a malicious site, it is possible to change the address bar so that the displayed location following navigation does not match the URL of the newly loaded page," Mozilla's security advisory warns. "This allows for spoofing attacks."

Sean Michael Kerner is a senior editor at eWEEK and Follow him on Twitter @TechJournalist.

Sean Michael Kerner

Sean Michael Kerner

Sean Michael Kerner is an Internet consultant, strategist, and contributor to several leading IT business web sites.