Hey,
I have a problem since this morning.
Sorry to hear you’re facing problems 
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In order to help you as quickly as possible, before clicking Create Topic please provide as much of the below as you can. Feel free to use a pastebin service for logs, otherwise either indent short log examples with four spaces:
example
Or for longer, use three backticks above and below the code snippet:
longer
example
here
Some or all of the below information will be requested if it isn’t supplied; for fastest response please provide as much as you can 
Nextcloud version (eg, 20.0.5): 21.0.1
Operating system and version (eg, Ubuntu 20.04): debian 10
Apache or nginx version (eg, Apache 2.4.25): nginx 1.20
PHP version (eg, 7.4): 8.0.3
The issue you are facing:
Is this the first time you’ve seen this error? (Y/N): Y
Steps to replicate it:
sudo -u www-data php -f /var/www/nextcloud/cron.php
PHP Fatal error: Allowed memory size of 2097152 bytes exhausted (tried to allocate 4096 bytes) in /var/www/nextcloud/3rdparty/composer/autoload_static.php on line 2530
The output of your Nextcloud log in Admin > Logging:
PASTE HERE
The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):
'passwordsalt' => 'SENSITIVE DATE REMOVED BY MOD [JK]',
'secret' => 'SENSITIVE DATE REMOVED BY MOD [JK]',
'trusted_domains' =>
array (
0 => 'SENSITIVE DATE REMOVED BY MOD [JK]',
1 => 'SENSITIVE DATE REMOVED BY MOD [JK]',
),
'datadirectory' => '/home/data',
'dbtype' => 'mysql',
'version' => '21.0.1.1',
'overwrite.cli.url' => 'https://xxx.xxx-xx.fr',
'dbname' => 'xxxx',
'dbhost' => 'localhost',
'default_langage' => 'fr',
'allow_user_to_change_display_name' => false,
'appstoreenabled' => true,
'dbport' => '',
'dbtableprefix' => 'oc_',
'mysql.utf8mb4' => true,
'dbuser' => 'xxxx',
'dbpassword' => 'xxx',
'installed' => true,
'instanceid' => 'SENSITIVE DATE REMOVED BY MOD [JK]',
'default_phone_region' => 'FR',
'activity_expire_days' => 365,
'activity_use_cached_mountpoints' => true,
'auth.bruteforce.protection.enabled' => true,
'blacklisted_files' =>
array (
0 => '.htaccess',
1 => 'Thumbs.db',
2 => 'thumbs.db',
),
'cron_log' => true,
'enable_previews' => true,
'enabledPreviewProviders' =>
array (
0 => 'OC\\Preview\\PNG',
1 => 'OC\\Preview\\JPEG',
2 => 'OC\\Preview\\GIF',
3 => 'OC\\Preview\\BMP',
4 => 'OC\\Preview\\XBitmap',
5 => 'OC\\Preview\\Movie',
6 => 'OC\\Preview\\PDF',
7 => 'OC\\Preview\\MP3',
8 => 'OC\\Preview\\TXT',
9 => 'OC\\Preview\\MarkDown',
),
'filesystem_check_changes' => 0,
'filelocking.enabled' => 'true',
'htaccess.RewriteBase' => '/',
'integrity.check.disabled' => false,
'knowledgebaseenabled' => false,
'log_rotate_size' => 104857600,
'logfile' => '/home/data/nextcloud.log',
'logtimezone' => 'Europe/Berlin',
The output of your Apache/nginx/system log in /var/log/____:
PASTE HERE
So I removed several sensitive data from your posting. Though you should regard your instance as being compromised, I’m afraid.
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