Feeds

Browser makers open local storage hole in HTML5

Bad implementation of disk space limits

Securing Web Applications Made Simple and Scalable

A slip-up in the implementation of HTML5 on Chrome, Opera and Internet Explorer can be exploited to fill users’ hard drives, according to a 22-year-old Web developer from Stanford.

Feross Aboukhadijeh has posted a proof-of-concept of the exploit here and a demonstration page here.

He explains that HTML5 is designed to allow bigger cookies than its predecessor standards. Up to 10 MB of local storage is permitted by the standard, but the standard also recommends that browsers place limits on how much storage is used. Browsers also need to watch out for sites trying to use subdomains or “affiliated domains” to get around the storage limits.

While the browsers Aboukhadijeh identifies implement the per-domain limits – 2.5 MB in Chrome, 5 MB in Firefox and Opera, 10 MB in IE – they don’t properly block the use of storage by affiliated domains.

Filldisk example site

The FillDisk demonstration site

“Thus, cleverly coded websites, like FillDisk.com, have effectively unlimited storage space on visitor’s computers”, he writes. Only recent versions of Firefox are unaffected, he says, because it has a better implementation of local storage (it does, however, work on older versions of Firefox, according to this author’s test).

Aboukhadijeh claims the proof-of-concept code will fill 1 GB every 16 seconds on a Macbook Pro Retina’s solid state drive.

While it’s not the scariest bug in the world, he says users of affected browsers should join together in filing bug reports so their browser vendors fix the bug. ®

Update: A commenter says Opera is unaffected. To test, I installed Opera 12.14 on OSX. The disk-filler gets as far as claiming 76 MB of space, after which Opera asked if I wanted to raise the storage limit - so I agree that it appears to work properly. I have not tested Opera on any other OS or version. ®

The smart choice: opportunity from uncertainty

More from The Register

next story
Mozilla fixes CRITICAL security holes in Firefox, urges v31 upgrade
Misc memory hazards 'could be exploited' - and guess what, one's a Javascript vuln
Manic malware Mayhem spreads through Linux, FreeBSD web servers
And how Google could cripple infection rate in a second
How long is too long to wait for a security fix?
Synology finally patches OpenSSL bugs in Trevor's NAS
Don't look, Snowden: Security biz chases Tails with zero-day flaws alert
Exodus vows not to sell secrets of whistleblower's favorite OS
Roll out the welcome mat to hackers and crackers
Security chap pens guide to bug bounty programs that won't fail like Yahoo!'s
HIDDEN packet sniffer spy tech in MILLIONS of iPhones, iPads – expert
Don't panic though – Apple's backdoor is not wide open to all, guru tells us
Researcher sat on critical IE bugs for THREE YEARS
VUPEN waited for Pwn2Own cash while IE's sandbox leaked
prev story

Whitepapers

Top three mobile application threats
Prevent sensitive data leakage over insecure channels or stolen mobile devices.
Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
Boost IT visibility and business value
How building a great service catalog relieves pressure points and demonstrates the value of IT service management.
Designing a Defense for Mobile Applications
Learn about the various considerations for defending mobile applications - from the application architecture itself to the myriad testing technologies.
Build a business case: developing custom apps
Learn how to maximize the value of custom applications by accelerating and simplifying their development.