Some of the changes in XF 2.2.6 include:

    Adjust file copying order of the one click upgrader to reduce issues with page breaks.
    Support youtube.com/shorts/{id} format URLs
    Change the CSS rules for inline spoilers to improve visibility
    Replace Accept header to use official v3 of GitHub API for connected account requests rather than its beta.
    Apply flood checking to thread create/reply pre-reg actions.
    If there is no editor/quick-reply element available, bail out of the quote-click JS handler early.
    Add some input placeholder styling to the stripe payment form.
    Prevent editing/display/use of some payment profiles when they are no longer active or the payment provider is no longer usable.
    When toggling comments with the profilePostCommentToggle style property enabled, ensure the editor placeholder is activated and, where possible, focus the editor.
    When getting global permission entries, process conditions correctly to only select the relevant records.
    Fix bad maxlength setting for warning definition titles and impose a maxlength for warning definition conversation titles.
    Prevent an error when trying to update reactions counts if we find a reaction content entry without a matching reaction definition.
    Implement the ability to add custom add/remove messages for the multi-quote button.
    Fix prefix function usage in alert/push_thread_reply_ban templates.
    Disable lightbox related output in RSS feeds.
    Allow member stats to be used in widgets regardless of overview_display option.
    Limit the size of each inline mod ****** to 3KB to avoid excessive header sizes.
    Add header 'Auto-Submitted: auto-generated' header by default to outgoing emails with the ability to override or unset if needed.
    Fix missing content type for contact form and protect against a PHP 8.0 issue if a content type phrase is empty.
    Fix unsupported operand error when validating a style archive if hashes.json fails to decode correctly.
    Add the ability to perform exact match email searches
    Remove duplicate itemprop attribute on a post's username link
    Validate usernames before trying to set them when creating threads as a guest
    Ensure phrases are properly returned as strings
    Wrap attachment action phrases that may not fit the thumbnail container
    Adjust description for the forum statistics widget
    Allow users to be reported regardless of their profile privacy settings
    Add a separate phrase for prefix searching on the admin panel's quick filter
    Ensure that non-ASCII characters are not in the local part of an email address.
    When analysing images, check image type against image extension map
    Allow alerts to be sent via an API super user key without a registered user.
    Validate a purchasable item exists during the callback stage of a payment.
    Ensure threads with a redirect thread type are included when batch updating threads or using a search forum
    Ensure post thread page action buttons are marked as nofollow
    Do not attempt to include a first_unread post in the API when the only unread posts in a thread are ignored.
    Ensure that phrases indirectly used in push and email templates use the correct ******.
    Make the process of canceling recurring PayPal subscriptions clearer if the user does not have a PayPal account.
    Improve performance of loading icons on the add-on list.
    Use a new system for shortening strings that contain BB code so that they will not be cut off in the middle of BB code markup.
    Do not allow transparent or system colors to be used in the color BB code.
    Ensure that italics in user content are displayed as expected when using CJK languages.
    Do not attempt to link URLs or email addresses that contain censored words.
    Properly process Stripe subscription refunds in the payment system.
    Do not display the "insert" option on attachments in contexts where they cannot be inserted into an editor.
    Improve the display of message attribution rows with a large amount of content on smaller devices.

The following public templates have had changes:

    account_upgrades
    alert_thread_reply_ban
    attachments.less
    bb_code.less
    core_datalist.less
    core_setup.less
    delete_confirm
    fa.css
    font_awesome_setup
    forum_overview_wrapper
    forum_post_thread_chooser
    forum_view
    helper_attach_upload
    helper_js_global
    message.less
    message_macros
    multi_quote_macros
    payment_cancel_recurring_paypal
    payment_initiate_stripe
    post_macros
    profile_post_macros
    push_thread_reply_ban
    reaction_item_profile_post
    reaction_item_profile_post_comment
    reaction_list_row
    search_forum_view
    setup_fa.less
    thread_view
    whats_new_posts