PHP: Fatal error when build docker image with composer

I saw this news about the serious vulnerability in composer which is PHP package management software.

https://www.bankinfosecurity.com/php-composer-flaw-that-could-affect-millions-sites-patched-a-16523

So, I wanted to update composer in my Dockerfile but I realized that I already specified the version as follows.

1curl -sS https://getcomposer.org/installer | php -- --install-dir=/usr/bin --filename=composer --version=1.10.16

Because it was a workaround for an error related to hirak/prestissimo which I did before. So, I deleted it and built the Docker image again but I got a different error as follows.

1#14 281.5  122/122 [============================] 100%  - Installing kylekatarnls/update-helper (1.2.0): Extracting archive
2#14 281.5 
3#14 281.5 Fatal error: Class UpdateHelper\ComposerPlugin contains 2 abstract methods and must therefore be declared abstract or implement the remaining methods (Composer\Plugin\PluginInterface::deactivate, Composer\Plugin\PluginInterface::uninstall) in …

It looks some problem about kylekatarnls/update-helper library. So, I searched about the library and I found a clue on GitHub.

https://github.com/kylekatarnls/update-helper/issues/7

So, I deleted composer.lock file and built the image again. Then the problem was solved. The above page said I need to delete the ‘vendor’ directory but it’s not necessary for docker build because it will be generated newly.