[Bug]: Wrong links and image URL in email (subfolder twice)

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

email notifications do not show the logo, because the image path is not correct.

I run nextcloud docker behind nginx reverse proxy. Nextcloud is running in a subdirectory: https://cloud.my-domain.org/mynextcloud/

The image URL in the notification is: <img class=3D"logo float-center" src=3D"https://cloud.my-domain.org/mynextcloud/mynextcloud/index.php/apps/theming/image/logo?useSvg=3D0&=v=3D260" alt=.... You can see that the subdirectory is twice in the path. If the email is an upload notification, the referenced files have this effect, too. Only the first link correctly references to the server URL (https://cloud.my-domain.org/mynextcloud/).

In my config.php, I have defined:

  'overwrite.cli.url' => 'https://cloud.my-domain.org/mynextcloud/',
  'overwritewebroot' => '/mynextcloud',
  'overwriteprotocol' => 'https',
  'htaccess.RewriteBase' => '/mynextcloud',
  'theme' => '',

The parameter htaccess.RewriteBase I have tried with => '/' and => '/mynextcloud'.

Because everything else is working fine, I believe that .htaccess and nginx config are good, and suspect the issue somewhere in my server/theming app.

Steps to reproduce

1. install nextcloud in a subdirectory behind an nginx reverse proxy
2. activate notification emails for shared folder uploads (or any other event)
3. upload a file to initiate a notification email
4. check email and contained header image or referenced file links

Expected behavior

The image is correctly shown and links to the uploaded files are working.

Nextcloud Server version

31

Operating system

Debian/Ubuntu

PHP engine version

PHP 8.3

Web server

Apache (supported)

Database engine version

MariaDB

Is this bug present after an update or on a fresh install?

None

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

{
    "system": {
        "memcache.local": "\\OC\\Memcache\\APCu",
        "apps_paths": [
            {
                "path": "\/var\/www\/html\/apps",
                "url": "\/apps",
                "writable": false
            },
            {
                "path": "\/var\/www\/html\/custom_apps",
                "url": "\/custom_apps",
                "writable": true
            }
        ],
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "overwrite.cli.url": "https:\/\/cloud.mydomain.org\/mynextcloud\/",
        "trusted_proxies": "***REMOVED SENSITIVE VALUE***",
        "trusted_domains": [
            "cloud.mydomain.org",
            "cloud.myotherdomain.de",
            "cloud.myotherdomain.fr"
        ],
        "overwritewebroot": "\/mynextcloud",
        "overwriteprotocol": "https",
        "htaccess.RewriteBase": "\/mynextcloud",
        "dbtype": "mysql",
        "version": "31.0.7.1",
        "installed": true,
        "mail_smtpmode": "smtp",
        "mail_smtpauthtype": "PLAIN",
        "loglevel": 0,
        "maintenance": false,
        "mail_from_address": "***REMOVED SENSITIVE VALUE***",
        "mail_domain": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpauth": 1,
        "mail_smtphost": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpname": "***REMOVED SENSITIVE VALUE***",
        "mail_smtppassword": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpport": "2525",
        "theme": "",
        "app_install_overwrite": [
            "polls",
            "unsplash",
            "social",
            "keeporsweep",
            "bookmarks_fulltextsearch",
            "bookmarks",
            "groupfolders",
            "tasks",
            "forms",
            "cookbook",
            "gpoddersync",
            "news"
        ],
        "ldapIgnoreNamingRules": false,
        "ldapProviderFactory": "OCA\\User_LDAP\\LDAPProviderFactory",
        "mysql.utf8mb4": true,
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "default_locale": "en_US",
        "default_phone_region": "DE",
        "memories.exiftool": "\/var\/www\/html\/custom_apps\/memories\/exiftool-bin\/exiftool-amd64-glibc",
        "mail_sendmailmode": "smtp",
        "simpleSignUpLink.shown": false
    }
}

List of activated Apps

Enabled:
  - activity: 4.0.0
  - admin_audit: 1.21.0
  - app_api: 5.0.2
  - bookmarks: 15.1.3
  - bruteforcesettings: 4.0.0
  - calendar: 5.3.8
  - circles: 31.0.0
  - cloud_federation_api: 1.14.0
  - comments: 1.21.0
  - contacts: 7.2.3
  - contactsinteraction: 1.12.0
  - cookbook: 0.11.3
  - cospend: 3.0.11
  - dav: 1.33.0
  - federatedfilesharing: 1.21.0
  - federation: 1.21.0
  - files: 2.3.1
  - files_downloadlimit: 4.0.0
  - files_external: 1.23.0
  - files_pdfviewer: 4.0.0
  - files_reminders: 1.4.0
  - files_sharing: 1.23.1
  - firstrunwizard: 4.0.0
  - flow_notifications: 2.0.1
  - forms: 5.1.2
  - gpoddersync: 3.12.0
  - groupfolders: 19.1.3
  - logreader: 4.0.0
  - lookup_server_connector: 1.19.0
  - mail: 5.1.10
  - news: 26.1.0
  - nextcloud_announcements: 3.0.0
  - notes: 4.12.2
  - notifications: 4.0.0
  - oauth2: 1.19.1
  - password_policy: 3.0.0
  - photos: 4.0.0
  - polls: 8.1.4
  - privacy: 3.0.0
  - profile: 1.0.0
  - provisioning_api: 1.21.0
  - recognize: 9.0.3
  - recommendations: 4.0.0
  - related_resources: 2.0.0
  - serverinfo: 3.0.0
  - settings: 1.14.0
  - sharebymail: 1.21.0
  - support: 3.0.0
  - systemtags: 1.21.1
  - tasks: 0.16.1
  - text: 5.0.0
  - theming: 2.6.1
  - twofactor_backupcodes: 1.20.0
  - twofactor_totp: 13.0.0-dev.0
  - updatenotification: 1.21.0
  - user_status: 1.11.0
  - viewer: 4.0.0
  - weather_status: 1.11.0
  - webhook_listeners: 1.2.0
  - workflowengine: 2.13.0
Disabled:
  - dashboard: 7.11.0 (installed 7.10.0)
  - encryption: 2.19.0 (installed 2.6.0)
  - files_automatedtagging: 2.0.0 (installed 2.0.0)
  - files_rightclick: 0.15.1 (installed 1.6.0)
  - files_trashbin: 1.21.0 (installed 1.8.0)
  - files_versions: 1.24.0 (installed 1.18.0)
  - maps: 1.6.0 (installed 1.6.0)
  - social: 0.7.0 (installed 0.7.0)
  - spreed: 21.1.2 (installed 21.1.2)
  - survey_client: 3.0.0 (installed 1.2.0)
  - suspicious_login: 9.0.1
  - twofactor_nextcloud_notification: 5.0.0
  - unsplash: 3.1.0 (installed 3.1.0)
  - user_ldap: 1.22.0 (installed 1.8.0)

Nextcloud Signing status

No errors have been found.

Nextcloud Logs

Additional info

No response

Reproduce the email notification with Nextcloud installed under /mynextcloud and inspect the generated logo and uploaded-file URLs. Trace URL generation in the theming and notification email paths, compare the first correct link with the duplicated subdirectory paths, and consider the issue done when both image and file links work from the subdirectory deployment.