* Added the $csp filter option (issue 5241).
* Requests sent by Shared/Service Workers are now matched in the context of the document that caused the worker to spawn, i.e. requests sent from the worker are now also subject to document-based whitelisting and domain-specific filters (issue 6543).
* Users with corrupted storage are now notified and instructed to reinstall Adblock Plus (issue 6599).
* Fixed: Videos (and other media elements) remained hidden if they previously attempt to stream a blocked resource (e.g. a pre-roll ad) but then changed their URL (issue 5899).
* Fixed: Exception rules for element hiding emulation filters were considered invalid when adding custom filters (issue 6139).
* Improved performance of element hiding emulation filters (issue 6437).
* Added support for pre-configurable preferences (issue 6474).
* Prevented third-party style sheets from breaking element hiding emulation filters (issue 6382).
* Worked around the limitations of notifications on Firefox (issue 6496).

* Improved "element hiding emulation filters":/development-builds/new-syntax-for-advanced-element-hiding-rules.
** Fixed false positives and related memory leak in dynamically changing documents (https://issues.adblockplus.org/ticket/5864).
** Added regular expression support for @:-abp-contains()@ (https://issues.adblockplus.org/ticket/6034).
** Added support for relative prefix within @:-abp-has()@ (https://issues.adblockplus.org/ticket/6296).
* Fixed empty error message when adding invalid custom filter (https://issues.adblockplus.org/ticket/6417).
* Removed the social media buttons from the ABP icon menu (https://issues.adblockplus.org/ticket/5613).
* Fixed a bug causing pages to be rendered blank when Web Components are enabled (https://issues.adblockplus.org/ticket/6441).
* Fixed the “Block element” dialog on Firefox 51 (https://issues.adblockplus.org/ticket/6113).
* Fixed links in the mobile Settings page, seen on Android (https://issues.adblockplus.org/ticket/6199).
* Fixed: Message about whitelisted domain is shown repeatedly on the Settings page (https://issues.adblockplus.org/ticket/6420).
* Improved performance when adding large number of custom filters (https://issues.adblockplus.org/ticket/6440).

* Improved "element hiding emulation filters":/development-builds/new-syntax-for-advanced-element-hiding-rules.
** Fixed false positives and related memory leak in dynamically changing documents (https://issues.adblockplus.org/ticket/5864).
** Added regular expression support for @:-abp-contains()@ (https://issues.adblockplus.org/ticket/6034).
** Added support for relative prefix within @:-abp-has()@ (https://issues.adblockplus.org/ticket/6296).
* Fixed empty error message when adding invalid custom filter (https://issues.adblockplus.org/ticket/6417).
* Removed the social media buttons from the ABP icon menu (https://issues.adblockplus.org/ticket/5613).
* Fixed a bug causing pages to be rendered blank when Web Components are enabled (https://issues.adblockplus.org/ticket/6441).
* Fixed the “Block element” dialog on Firefox 51 (https://issues.adblockplus.org/ticket/6113).
* Fixed links in the mobile Settings page, seen on Android (https://issues.adblockplus.org/ticket/6199).
* Fixed: Message about whitelisted domain is shown repeatedly on the Settings page (https://issues.adblockplus.org/ticket/6420).
* Improved performance when adding large number of custom filters (https://issues.adblockplus.org/ticket/6440).

* Fixed the “Block element” tool for Windows users.
* Fixed blocking of WebRTC connections on websites using CSP security mechanism, works in Firefox 58 and higher now.
* Made sure that filter list downloads and other requests performed by the extension cannot be blocked.
* Fixed subscription link handling for Windows users.
* Fixed a bug which caused the mobile options page to be zoomed incorrectly.
* Fixed a bug which caused the desktop popup window to open instead of the mobile options page with Firefox 57 for Android and higher.
* Improved our Developer Tools panel, fixing a bug which prevented viewing the requested resource.
* Improved the layout of the options page and added a warning for users who subscribe to both the Easy Privacy and Acceptable Ads filter lists.
* Firefox 50 is no longer supported, the options page is essentially broken there without a way to fix it.

This release adds many translations that were missing in the Adblock Plus 3.0 release. There are no changes beyond that.

With Mozilla disallowing classic extensions in Firefox 57, Adblock Plus 3.0 is our first version based on the Web Extensions framework. The significant changes introduced here are unfortunate but sadly unavoidable. This is particularly visible in the user interface:

* The ABP icon in the toolbar will now display the number of blocked ads (optional, can be disabled). This replaces the status information in the tooltip.
* The toolbar icon will no longer open a native menu but rather a pop-up. This one uses an old design, we want to improve it soon.
* The options page is not a native dialog but a web page now. It should be easier to use, but it is lacking much of the functionality that Firefox users got used to. We plan to add more functionality to it in future.
* The issue reporter works mostly the same as it did before, but it won't flag common issues locally at this point. Also, it will collect less information than it did before. We'll keep improving it.
* The "Block element" dialog offers less assistance than it did before, we will improve that as well.

As to the good news:

* We largely fixed the performance degradation which has been an issue since we switched to a different storage format with Adblock Plus 2.9. The root issue is gong to be addressed in Firefox 57.
* The experimental element hiding emulation syntax is now available in Firefox as well.
* Blocking WebRTC connections is also possible in Firefox now.

With this being a massive change, there are some known issues left which should be addressed in another release soon:

* The "Block element" dialog doesn't work in Firefox 57 under some circumstances.
* On Firefox 57 for Android, the Adblock Plus menu item opens the (partly dysfunctional) pop-up rather than the options page
* In older Firefox versions such as Firefox 50, saving custom filters won't update the list and you need to reload the options page to see your changes.
* abp:subscribe links sometimes won't work in Firefox 57.

* Counting filter hits is now disabled by default, to alleviate performance issues experienced by some users (can be enabled again under "Options" if necessary).
* Fixes regression in Adblock Plus 2.9, extension being broken in Thunderbird and SeaMonkey.

We are still trying to reproduce issues experienced by some Firefox users, with filter changes not being saved. We are also still looking into ways to address performance issues caused by using Web Extensions storage starting with Adblock Plus 2.0.

This release lays important groundwork for the Web Extensions migration. The way Adblock Plus stores its data has changed drastically, though for users everything should stay exactly the same. The new location of your filters and subscriptions is the browser-extension-data/{d10d0bf8-f5b5-c8b4-a8b2-2b9879e08c5d}/storage.js file in your Firefox profile, the same data will be used by the Adblock Plus build based on the Web Extensions platform once it is ready.

Additional changes

* The hidden data_directory and please_kill_startup_performance preferences have been removed.
* It is now possible to use { and } in CSS property filters.

* Improved the way CSS property filters match elements.
* Made sure that element hiding rules don't affect browser's and extensions' special pages, this regressed with Adblock Plus 2.8.
* Fixed blockable items list slowing down page loading.
* Pop-ups using data: URLs and similar unusual schemes can be blocked now.
* When selecting keyboard shortcuts, more shortcut keys already in use by the browser can be recognized. This will change the shortcut key to show Blockable items list from Ctrl/Cmd-Shift-V to Ctrl/Cmd-Shift-U for pretty much everybody.

Fixed a regression in Adblock Plus 2.8, filters weren't loaded completely for users who enabled please_kill_startup_performance preference.

* Reworked element hiding functionality, improved its performance and eliminated unexpected side-effects.
* There is a special $websocket type option now to block WebSocket requests, the type was previously considered to be other here.
* Our toolbar icon will look better on high-resolution screens.
* Removed feature selection from the first-run page until the features can be removed similarly easily.
* Hits for CSS property filters which were introduced in the previous release are being counted now.
* Fixed: CSS property filters applied even when Adblock Plus was disabled everywhere.
* Fixed: A regression in pop-up blocking functionality caused websites to be mistakenly considered pop-ups under some circumstances.
* Corrected handling of frames with srcdoc attribute.
* Fixed and improved search functionality in Filter Preferences, was partially broken in Firefox nightly builds.

This release adds support for the experimental CSS properties syntax. This support isn't complete yet, most important issue being that hits are not counted for CSS properties filters.

Additional changes:

* Fixed issues that Adblock Plus could potentially cause on Firefox startup.
* Some first-run page optimizations.
* Cleaned up internal messaging approach.

This release works around some obscure Firefox bugs which Adblock Plus has been triggering since Adblock Plus 2.7 release. Additional changes:

* Closed a pop-up blocking loophole misused by some websites.
* Fixed tooltip display for very long filters.

* Fully compatible with the upcoming multi-process mode in Firefox, no longer relying on backwards compatibility hacks in Firefox.
* Improved performance: patterns.ini was being saved way more often than necessary.
* $ping filter option is back and will especially apply to requests sent via navigator.sendBeacon().
* Requests produced by <img srcset> and <picture> will be assigned type image.
* Requests produced by the Fetch API will be assigned type xmlhttprequest.
* genericblock and generichide types will no longer show up in the filter assistant.
* Removed non-standard JavaScript syntax, which caused warnings in Firefox Aurora and Nightly builds.
* Fixed: Previously disabled and removed filter is still disabled when added back.
* Fixed regressions in previous release:
** Pop-up blocking doesn't catch redirects to a different domain.
** Issue Reporter gets stuck if filter subscriptions need updating.
** Screenshot marker in Issue Reporter is no longer red.
** Fixed image preview in Blockable Items tooltip.

* Addressed most of the issues affecting Adblock Plus in the latest Firefox pre-release builds, particularly when multi-process mode is enabled in Firefox settings.
* If pop-ups are blocked after the redirect, the pop-up window will actually be closed and not merely prevented from loading.
* The diagnostic page under chrome://adblockplus/content/errors.html has been removed, it was of very limited use.

For a list of remaining issues see https://adblockplus.org/releases/adblock-plus-27-for-firefox-released

Worked around a critical issue in Firefox nightly builds.

We are aware of an issue breaking Adblock Plus user interface in the latest Firefox nightly builds, this will be fixed in the next release. There is also an "issue related to element hiding functionality in Firefox 43 and above":https://issues.adblockplus.org/ticket/3108, this one will also be addressed in the next release.

Changes in this release:

* Added $generichide and $generic block filter options.
* Improved first-run display on small screens, especially on mobile devices.
* Fixed: Findbar in Filter Preferences is being triggered when trying to edit filters.
* Fixed: Ctrl+F wasn't working as expected when the findbar was already open.
* Fixed: Filter composer's "Advanced view" button was broken in Firefox nightly builds.
* Fixed: Anti-Adblock warning shouldn't show up when Adblock Plus is disabled.
* Fixed: Anti-Adblock warning shouldn't be triggered by frames.

* Fixed: Findbar in Filter Preferences was slightly broken when using Firefox 42 and above.
* Fixed: Notification pop-up shouldn't disappear if somebody clicks outside it.
* Fixed: Toolbar icon broken in SeaMonkey 2.40 and above.
* Added promotional message for Adblock Browser to the first-run page.

* suppress_first_run_page preference introduced by previous release can now be preconfigured by machine administrators via setting extensions.adblockplus.preconfigured.suppress_first_run_page Firefox preference.
* Issue reporter: Made sure there is always enough space to display report data.
* Issue reporter: No longer intercepting right-clicks on the resulting report link, only left- and middle-clicks result in the report being opened.
* Implemented an alternative format for subscription links that is easier to use in forums or emails: https://subscribe.adblockplus.org/?location=foo instead of abp:subscribe?location=foo.
* Fixed subscription links in multi-process Firefox
* Added global opt-out for notifications.
* Notifications are shown immediately after download rather than waiting for a browser restart.
* Removed inconsistent behavior (breaks backwards compatibility): exception rules starting with http:// or https:// no longer imply $document option.
* Reduced the initial delay for filter lists and notification updates after browser startup.
* First-run page: Fixed social buttons being broken starting with Firefox 38.

* Slightly optimized performance, domain-specific filters will no longer affect overall performance.
* Added extensions.adblockplus.suppress_first_run_page preference to allow administrators disable the first-run page if Adblock Plus is installed globally.
* Fixed: $elemhide filter option doesn't consider website signatures correctly.

* Fixed issue with search functionality in Filter Preferences (affecting Firefox 36 and above).
* Improved ABP icons and logo.

* Removed "Hide placeholders of blocked elements" option from the user interface.
* Fixed: First-run page broken in Firefox nightlies if E10S is enabled.
* Fixed first-run page layout for right-to-left languages.
* Fixed: "Adblock Warning Removal List" is being displayed as the selected list on Firefox Mobile.
* Fixed: "Disable on site" doesn't always show up on Firefox Mobile.

Adapted to an API change in current Firefox nightlies causing Adblock Plus to break.

* Fixed: Element hiding exceptions are broken by changes in Firefox 34 and Firefox 35.
* Fixed: Blocking via context menu won't always suggest blocking the most recent request.
* Fixed: Issue reporter will complain about too many filter lists even when these filter lists are "special" like the anti-adblock list.
* Fixed: Disabling filters via space bar no longer works in preferences.
* Fixed: Sharing Adblock Plus from the first-run page won't work if the Anti-Social list is enabled.
* Fixed: Anti-Adblock warning will sometimes appear on websites without any anti-adblock behavior.
* Made $sitekey option behavior more consistent, it can be used similarly to $domain now rather than whitelisting complete websites only.

* Made sure that data is always written to disk immediately whenever filter hit counts are reset.
* Fixed: Moving filters with Ctrl-Up/Down doesn't work in Firefox 30 and above.
* Fixed: Find functionality in the preferences doesn't indicate that the search pattern wasn't found (Firefox 29 and above).
* Fixed: User isn't informed about anti-adblock warnings on websites producing them.
* Fixed: Blockable items aren't refreshed on tab change in SeaMonkey.
* Fixed: "Disable on this page only" doesn't work correctly if the address ends with #.

* Worked around a Firefox bug preventing filters from being saved in Firefox 22 and older on Windows.
* Default context menu is no longer overridden on the toolbar icon if a left click would result in the same action already.
* Fixed: Adblock Plus toolbar icon appears delayed.
* Fixed: Warning shows up in console concerning use of setUserData (only resolved for Firefox 32 and higher).
* Fixed: Bogus tooltip on the "Slow" column in Filter Preferences.

* Made sure Adblock Plus initialization doesn’t delay Firefox startup.
* Switched to a faster way to access Adblock Plus data on disk.
* Fixed regression in Adblock Plus 2.5.1: Adblock Plus initialization takes longer for each new window opened.
* Fixed: Firefox Sync integration sometimes won’t work.
* Fixed: Filter search in Filter Preferences was broken in newer Firefox versions.
* Fixed: Wrong button type displayed for Adblock Plus immediately after customizing toolbar in Firefox 29 and above.
* Fixed: Homepage link is displayed in Filter Preference even if the subscription doesn’t define a homepage.
* Fixed: Pop-up blocker won't work in some scenarios.

* Added a dialog that shows up the first time a user visits a website which shows an anti adblock message, asking whether these should be blocked
* Fixed: Pipe character in filters interpreted wrong under some circumstances
* Fixed: Share window on first-run page doesn't appear

* Added support for the upcoming Firefox Australis theme.
* Default icon location is the navigation toolbar again (add-on bar is going away).
* Fixed image preview in the list of blockable items.
* Fixed keyboard shortcut on Mac OS X (Control key was used instead of Command).
* Fixed: Changes to Adblock Plus options didn't always persist.

* Improved first-run page
* Fixed: Adblock Plus icon wasn't showing up on browser startup for some users
* Fixed: Redirect blocking wasn't working in current Firefox versions
* Fixed: Issue reporter fails to process some console errors
* Fixed: Adblock Plus fails to start up when updating in current Firefox nightly builds (workaround for bug 924340)