Sometimes a problem with Firefox may be a result of malware installed on your computer, that you may not be aware of.

You can try these free programs to scan for malware, which work with your existing antivirus software:

• Microsoft Safety Scanner
• MalwareBytes' Anti-Malware
• TDSSKiller - AntiRootkit Utility
• Hitman Pro
• ESET Online Scanner

Microsoft Security Essentials is a good permanent antivirus for Windows 7/Vista/XP if you don't already have one.

Further information can be found in the Troubleshoot Firefox issues caused by malware article.

Did this fix your problems? Please report back to us!

Maybe you didn't read the entire post. I'm running LINUX. Not that Microsoft garbage. It's VERY hard to sneak unknown malware onto somebody else's Linux box. Nearly impossible in fact. That's why I'm running Linux.

Here's the Troubleshooting Data (again) which shows you what I'm running here:

Application Basics

Name: Firefox Version: 25.0.1 User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:25.0) Gecko/20100101 Firefox/25.0

Extensions

Name: Adblock Plus Version: 2.4 Enabled: true ID: {d10d0bf8-f5b5-c8b4-a8b2-2b9879e08c5d}

Name: Hide Tab Bar With One Tab Version: 1.2beta3 Enabled: true ID: {e5bbc237-c99b-4ced-a061-0be27703295f}

Name: LastPass Version: 3.0.12 Enabled: true ID: support@lastpass.com

Name: Troubleshooter Version: 1.1a Enabled: true ID: troubleshooter@mozilla.org

Name: Ubuntu Firefox Modifications Version: 2.8 Enabled: true ID: ubufox@ubuntu.com

Name: Xmarks Version: 4.2.1 Enabled: true ID: foxmarks@kei.com

Important Modified Preferences

accessibility.typeaheadfind.flashBar: 0 browser.cache.disk.capacity: 358400 browser.cache.disk.smart_size_cached_value: 358400 browser.cache.disk.smart_size.first_run: false browser.cache.disk.smart_size.use_old_max: false browser.places.smartBookmarksVersion: 4 browser.sessionstore.restore_on_demand: false browser.sessionstore.upgradeBackup.latestBuildID: 20131115105349 browser.startup.homepage: http://www.google.ca/ browser.startup.homepage_override.buildID: 20131115105349 browser.startup.homepage_override.mstone: 25.0.1 browser.tabs.loadInBackground: false dom.mozApps.used: true extensions.lastAppVersion: 25.0.1 network.cookie.prefsMigrated: true network.protocol-handler.app.ed2k: ed2k_gui places.database.lastMaintenance: 1386381833 places.history.expiration.transient_current_max_pages: 92068 plugin.disable_full_page_plugin_for_types: application/pdf plugin.importedState: true privacy.donottrackheader.enabled: true privacy.sanitize.migrateFx3Prefs: true storage.vacuum.last.index: 1 storage.vacuum.last.places.sqlite: 1386021194

Graphics

Adapter Description: NVIDIA Corporation -- GeForce GT 430/PCIe/SSE2 Device ID: GeForce GT 430/PCIe/SSE2 Driver Version: 4.4.0 NVIDIA 331.20 GPU Accelerated Windows: 0/1 Basic Vendor ID: NVIDIA Corporation WebGL Renderer: NVIDIA Corporation -- GeForce GT 430/PCIe/SSE2 windowLayerManagerRemote: false AzureCanvasBackend: cairo AzureContentBackend: none AzureFallbackCanvasBackend: none AzureSkiaAccelerated: 0

JavaScript

Incremental GC: true

Accessibility

Activated: false Prevent Accessibility: 0

Library Versions

NSPR Expected minimum version: 4.10.2 Version in use: 4.10.2

NSS Expected minimum version: 3.15.3 Basic ECC Version in use: 3.15.3 Basic ECC

NSSSMIME Expected minimum version: 3.15.3 Basic ECC Version in use: 3.15.3 Basic ECC

NSSSSL Expected minimum version: 3.15.3 Basic ECC Version in use: 3.15.3 Basic ECC

NSSUTIL Expected minimum version: 3.15.3 Version in use: 3.15.3

You can try Firefox safe mode to see if addons are the issue.

• Diagnose Firefox issues using Troubleshoot Mode

Unity Menu Bar (At the top, of course) => Help => Restart With Addons disabled.

Note that if you find the Ubufox addon to be causing you your troubles, you would need to uninstall it from the package manager (apt/synaptic).

Did you check the connection settings?

• Edit > Preferences > Advanced > Network : Connection > Settings
• https://support.mozilla.org/kb/Options+window+-+Advanced+panel

If you do not need to use a proxy to connect to internet then try to select "No Proxy" if "Use the system proxy settings" or one of the others do not work properly.

See "Firefox connection settings":

• https://support.mozilla.org/kb/Firefox+cannot+load+websites+but+other+programs+can

Sorry, Already checked proxy settings just in case there's some shenanigans about. Good thinking though.

I ditched Unity in favour of Cinnamon, and running in Safe Mode still presents the same irritation.

I'm starting to wonder if it's not Firefox, but MediaFire itself. Background: I play Minecraft (who doesn't these days?), and I use MCEdit, and a lot of people share their MCEdit exports (.schematic files) on MediaFire, but MediaFire is the only site that seems to be giving me trouble.

Guess maybe they've buried some kind of pop-up work-around in all that Javascript and I'll just have to suck it up (or continue to add places to my HOSTS to block the source, even if I can't block the window).

I don't use it myself, but there is a pop-up specific add-on for Adblock Plus that might be designed to deal with this issue:

https://addons.mozilla.org/en-US/firefox/addon/adblock-plus-pop-up-addon/

That did the trick! Thanks!