WordPress on Wednesday escalated its conflict with WP Engine, a hosting provider, by blocking the latter’s servers from accessing WordPress.org resources – and therefore from potentially vital software updates.

WordPress is an open source CMS which is extensible using plugins. Its home is WordPress.org, which also hosts resources such as themes and plugins for the CMS. A vast ecosystem of plugins exists from numerous suppliers, but WordPress.org is the main source.

Many WordPress users rely on several plugins. Preventing WP Engine users from accessing plugin updates is therefore serious, as it could mean users can’t update plugins that have security issues, or other fixes.

WordPress co-founder and CEO Matt Mullenweg recently called WP Engine a “cancer” and accused it of profiting from WordPress without contributing to development of the CMS. Mullenweg has sought to have WP Engine pay trademark license fees – a move he feels would represent a financial contribution commensurate with the benefits it derives from the project.

WP Engine doesn’t want or intend to pay.

Mullenweg argued that if WP Engine won’t pay, it should not be able to benefit from resources at WordpPress.org.

“WP Engine wants to control your WordPress experience. They need to run their own user login system, update servers, plugin directory, theme directory, pattern directory, block directory, translations, photo directory, job board, meetups, conferences, bug tracker, forums, Slack, Ping-o-matic, and showcase,” Mullenweg wrote in a WordPress.org post announcing the ban. “Their servers can no longer access our servers for free.”

The denial of service, which follows mutual cease and desist letters, has been noted in the WP Engine incident log. “WordPress.org has blocked WP Engine customers from updating and installing plugins and themes via WP Admin,” the venture-backed web hosting vendor wrote on its status page.

In the post announcing the ban, Mullenweg directed WP Engine customers to contact WP Engine support if they’re having trouble with their WordPress websites.

WP Engine did not immediately respond to a request for comment.

Among WordPress users posting to Reddit, not everyone is on board with Mullenweg’s war against WP Engine. There’s discussion of a WordPress fork, and pushback against the WP Engine block. ®