Update October 15, 2015: ZDNet reports a critical Flash vulnerability that affects all versions of the browser plug-in, so we are reposting this story and adding instructions for disabling flash in Microsoft Edge.
Flash has been found to have multiple zero-day security flaws, which Adobe has been hurriedly patching. But Mozilla Firefox is currently blocking Flash in response, and Facebook's security chief is calling for an end to Flash altogether. If you really want to keep using Flash, update it immediately. But it might be a better idea to go into your desktop browser settings and shut down this media streaming tool, at least for now. Devices using Google's Android operating system do not have Flash pre-installed, and of course Apple has long banned Flash from iOS devices, so you only need to tweak your Windows and Mac browsers. Not sure if Flash is installed? Go to Adobe's Flash Player page and click the Check Now button.
Disable Flash in Microsoft Edge
1. Open Edge by clicking the blue E on your taskbar or desktop.
2. Click the More Actions button, which is near the upper right-hand corner and has three dots in a horizontal line on it.
3. Click Settings at the bottom of the More Actions menu.
4. Scroll down and click the View Advanced Settings button toward the bottom of the Settings menu.
5. Toggle Use Adobe Flash Player from on to off.
In Edge, this change will take effect automatically. If you already have a page open in Edge with Flash elements loaded, you may need to refresh the page (press F5 on your keyboard) to see it without Flash elements.
Disable Flash in Mozilla Firefox
Flash is not pre-installed in Firefox, and at the moment Firefox is blocking it by default. But if you have it and want to turn it off longer term, follow these steps:
1. Click the hamburger button (with three horizontal stacked lines) in the upper right hand-corner of the browser window.
2. Click the Add-ons button and then Plugins in the left menu.
3. Go to Shockwave Flash, click the Always Activate button, and click Never Activate. (If you need this plug-in for work purposes, you can also choose Ask to Activate.)
If the version of Flash that's linked to Firefox is out of date, you can update it using this browser-based tool from Mozilla, which will also check all your other installed add-ons for issues.
Disable Flash in Google Chrome
Flash is integrated into Chrome, so we'll disable a setting instead of an add-on.
1. Click the address bar at the top of your browser and type about:plugins.
2. Scroll down to Adobe Flash Player and click the Disable link.
Disable Flash in Apple Safari (OS X)
Apple doesn't put Flash on its iOS devices, but you may have it installed on your MacBook or iMac.
1. Go to the menu bar at the top of the Safari window.
2. Select Safari and click Preferences.
3. Click the Security button, then Internet Plug-ins: Website Settings.
4. Select Adobe Flash Player from the menu on the left.
5. Click the drop-down menu labeled "When visiting other websites" (just above the Done button) and choose Block.
Disable Flash in Internet Explorer 11
1. Click the gear icon in the upper right-hand corner.
2. Select "Manage add-ons."
3. In the Show drop-down menu, select "All add-ons."
4. Click the item labeled Shockwave Flash Object and click the Disable button in the lower right-hand corner of the window.
If you're worried that you won't be able to watch YouTube videos after disabling Flash, you can set your browser to use the site's HTML5 streaming instead. First, go to YouTube's HTML5 page to see if you're already using HTML5 by default. If not, click the button labeled "Request the HMTL5 player" to make the switch.