Do you have Kaspersky Internet Security 2016 or 2017? For 2016, this should have been fixed in the February update. No idea about 2017 but presumably should work out of the box.

What version of the extension do you have? You can check on the Add-ons page, either:

• Ctrl+Shift+a (Mac: Command+Shift+a)
• "3-bar" menu button (or Tools menu) > Add-ons

In the left column, click Extensions. Then on the right side scroll down to the "grayed out" extensions and check Kaspersky Protection. If the version number is not visible immediately, click the tiny More link to its detail page.

Mozilla Firefox Version 48.0.2 Kaspersky 2016 4.6.2-40 Kaspersky Protection Last updated May 27, 2016

Windows 7 - up to date

Hmm, I don't know how the program and extension version numbers line up.

In other recent threads where users shared their extension lists, I have seen these versions:

• Kaspersky Protection 4.6.3-7 (light_plugin_ACF0E80077C511E59DED005056C00008@kaspersky.com) [on Windows 10]
• Kaspersky Protection 4.6.3-9 (light_plugin_ACF0E80077C511E59DED005056C00008@kaspersky.com) [on Windows 8.1]
• Kaspersky Protection 5.0.130-0-20160620125320 (light_plugin_F6F079488B53499DB99380A7E11A93F6@kaspersky.com) [on Windows 7 -- maybe this is KIS 2017?]

In case the Add-ons page is not showing duplicates, could you check the Troubleshooting Information page. Either:

• "3-bar" menu button > "?" button > Troubleshooting Information
• (menu bar) Help > Troubleshooting Information
• type or paste about:support in the address bar and press Enter

Scroll down to the Extensions heading and check the table that follows to see whether Firefox is using an older version as well as the one you found on the Add-ons page.

Thanks for you help. I will check on upgrading to Kaspersky 2017 and see if that resolves the issue. Again thanks for taking the time to respond.