Why Browser Extensions Are Dangerous

UPDATE: Read more here about Chrome security issues

Regardless of browser-type used, I’ve always been **extremely** cautious about loading extensions, especially if they’ve been created in God-knows-what-country and ask for permissions that are worse than leaving your front door open with the key in the lock!

There have been a number of compromised extensions recently in Chrome (see Attackers Go on a Chrome Extension Hijacking Spree” – Several More Compromised) and other browsers are not immune. But it’s this recent spate of Chrome-based extension compromises that is the biggest worry.

How-To Geek just published Browser Extensions Are a Privacy Nightmare: Stop Using So Many of Them and it is absolutely worth a read, especially with warnings like this:

“Modern web browsers like Google Chrome and Microsoft Edge have a permission system for extensions, but many extensions require access to everything so they can work properly. Even an extension that just requires access to one website could be dangerous, however. For example, an extension that modifies Google.com in some way will require access to everything on Google.com, and therefore have access to your Google account—including your email.

These aren’t just cute, harmless little tools. They’re tiny programs with a huge level of access to your web browser, and that makes them dangerous. Even an extension that only does a minor thing to web pages you visit may require access to everything you do in your web browser.”

So either don’t load extensions or be very, very, very careful when you do so.

To my point about Google Chrome being compromised, here is an update on Thursday, 8/17/17 from an email I received from US-CERT, the United States Computer Emergency Readiness Team:

MS-ISAC CYBERSECURITY ADVISORY

MS-ISAC ADVISORY NUMBER: 2017-068 – UPDATED

DATE(S) ISSUED: 07/26/2017 (08/17/2017 – UPDATED)

SUBJECT: Multiple Vulnerabilities in Google Chrome Could Allow for Arbitrary Code Execution

OVERVIEW:

Multiple vulnerabilities have been discovered in Google Chrome, the most severe of which could allow for arbitrary code execution. Google Chrome is a web browser used to access the Internet. These vulnerabilities can be exploited if a user visits, or is redirected to, a specially crafted web page. Successful exploitation of the most severe of these vulnerabilities could allow an attacker to execute arbitrary code in the context of the browser, obtain sensitive information, bypass security restrictions and perform unauthorized actions, or cause denial-of-service conditions.

THREAT INTELLIGENCE:

There are currently no reports of these vulnerabilities being exploited in the wild.

AUGUST 17 – UPDATED THREAT INTELLIGENCE:

An additional vulnerability has been discovered in Google Chrome, which could allow for remote code execution. Proof of Concept code is available that reproduces the vulnerability. Affected versions of Google Chrome are 59 and earlier. Google announced no patches will be provided for this vulnerability and the only mitigation is to upgrade to the current and latest version, version 60.

SYSTEMS AFFECTED:

• Google Chrome prior to 60.0.3112.78

RISK:

Government:

• Large and medium government entities: High
• Small government entities: Medium

Businesses:

• Large and medium business entities: High
• Small business entities: Medium

Home users: Low

TECHNICAL SUMMARY:

Multiple vulnerabilities have been discovered in Google Chrome, the most severe of which could allow for arbitrary code execution. These vulnerabilities can be exploited if a user visits, or is redirected to, a specially crafted web page. Details of the vulnerabilities are as follows:

• Use after free in IndexedDB (CVE-2017-5091).
• Use after free in PPAPI (CVE-2017-5092).
• UI spoofing in Blink (CVE-2017-5093).
• Type confusion in extensions (CVE-2017-5094).
• Out-of-bounds write in PDFium. (CVE-2017-5095).
• User information leak via Android intents (CVE-2017-5096).
• Out-of-bounds read in Skia (CVE-2017-5097).
• Use after free in V8. (CVE-2017-5098)
• Out-of-bounds write in PPAPI. (CVE-2017-5099)
• Use after free in Chrome Apps. (CVE-2017-5100)
• URL spoofing in OmniBox. (CVE-2017-5101)
• Uninitialized use in Skia. (CVE-2017-5102)
• Uninitialized use in Skia. (CVE-2017-5103)
• UI spoofing in browser. (CVE-2017-5104)
• Pointer disclosure in SQLite. (CVE-2017-7000)
• URL spoofing in OmniBox. (CVE-2017-5105)
• URL spoofing in OmniBox. (CVE-2017-5106)
• User information leak via SVG. (CVE-2017-5107)
• Type confusion in PDFium. (CVE-2017-5108)
• UI spoofing in browser. (CVE-2017-5109)
• UI spoofing in payments dialog. (CVE-2017-5110)

Successful exploitation of the most severe of these vulnerabilities could allow an attacker to execute arbitrary code in the context of the browser, obtain sensitive information, bypass security restrictions and perform unauthorized actions, or cause denial-of-service conditions.

RECOMMENDATIONS:

We recommend the following actions be taken:

• Apply appropriate patches provided by Google to vulnerable systems immediately after appropriate testing.
• Run all software as a non-privileged user (one without administrative privileges) to diminish the effects of a successful attack.
• Remind users not to visit un-trusted websites or follow links provided by unknown or un-trusted sources.
• Inform and educate users regarding the threats posed by hypertext links contained in emails or attachments especially from un-trusted sources.
• Apply the Principle of Least Privilege to all systems and services.

REFERENCES:

Google:

https://chromereleases.googleblog.com/2017/07/stable-channel-update-for-desktop.html

CVE:

• http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5091
• http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5092
• http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5093
• http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5094
• http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5095
• http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5096
• http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5097
• http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5098
• http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5099
• http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5100
• http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5101
• http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5102
• http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5103
• http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5104
• http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5105
• http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5106
• http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5107
• http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5108
• http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5109
• http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5110
• http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-7000

August 17 – UPDATED REFERENCES:

Securiteam: https://blogs.securiteam.com/index.php/archives/3379

Helpnetsecurity: https://www.helpnetsecurity.com/2017/08/17/google-chrome-remote-code-execution-flaw/

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SOC@cisecurity.org – 1-866-787-4722

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