Google this week released Chrome 76 to the stable channel with 43 security fixes inside, as well as with other safety and privacy enhancements.
Sixteen of the 43 security fixes are for vulnerabilities that were reported by external researchers. These include 5 bugs that are rated High severity, 4 assessed as Medium risk, and 7 considered Low severity.
The most important of the flaws in a use-after-free in offline page fetcher. Tracked as CVE-2019-5850, the issue was reported by Brendon Tiszka, who received a $10000 bug reward for the finding.
Next in line is CVE-2019-5860, a use-after-free in PDFium, which brought an anonymous researcher a $6000 bug reward. Google awarded $3000 each to the researchers who found two other High risk vulnerabilities, namely CVE-2019-5853, a memory corruption in regexp length check, and CVE-2019-5851, a use-after-poison in offline audio context.
The Internet search giant has yet to reveal the bug bounty reward set for the fifth High severity issue (CVE-2019-5859: res: URIs can load alternative browsers).
The first of the Medium risk issues addressed in Chrome 76 is CVE-2019-5856: insufficient checks on filesystem: URI permissions. For this bug, Google paid a $5000 reward to Yongke Wang of Tencent’s Xuanwu Lab.
No bounty reward was paid for the next two Medium severity issues (CVE-2019-5863: Use-after-free in WebUSB on Windows, and CVE-2019-5855: Integer overflow in PDFium). The reward for the fourth Medium risk flaw (CVE-2019-5865: Site isolation bypass from compromised renderer) hasn’t been revealed yet.
The Low risk vulnerabilities addressed are CVE-2019-5858: Insufficient filtering of Open URL service parameters, CVE-2019-5864: Insufficient port filtering in CORS for extensions, CVE-2019-5862: AppCache not robust to compromised renderers, CVE-2019-5861: Click location incorrectly checked, CVE-2019-5857: Comparison of -0 and null yields crash, CVE-2019-5854: Integer overflow in PDFium text rendering, and CVE-2019-5852: Object leak of utility functions.
Chrome 76 also addresses a loophole that allowed sites to detect people who browsing in Incognito Mode by checking whether the FileSystem API is disabled (which happens by default in Incognito Mode). While the idea was to prevent leaving traces of activity on devices, sites abused the loophole to deliver a different experience to users.
“The change will affect sites that use the FileSystem API to intercept Incognito Mode sessions and require people to log in or switch to normal browsing mode, on the assumption that these individuals are attempting to circumvent metered paywalls,” Google said.
Another major security improvement in Chrome 76 is the disabling of Flash content by default, instead of asking the user whether they want to allow it to run or not. However, users can change the default setting and can also whitelist specific sites to ensure they can always run the plugin.
Mozilla is also planning a similar move in Firefox, which is expected to completely disable Flash when an updated version is released in the next several days.