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Nethemba security analysis graphic headed Backdoor via UpdraftCentral, showing an updraftcentral_client_log window with a probe.central.updraftplus.com notice, a plugin.upload_plugin command, the attacker IP 43.250.53.42, the Load Stack 35C / PixelBinder plugin and the WP-CLI command wp option delete updraft_central_localkeys.
Screenshot: Nethemba, Backdoor via UpdraftCentral security-analysis graphic, Oct 19, 2026 (fair use).

Response

TeamUpdraft Confirms Stolen UpdraftCentral Keys Let Attackers Push Backdoor Plugins Onto Connected WordPress Sites, and Sites Must Delete the Keys Themselves

An attacker who held valid UpdraftCentral Cloud dashboard keys pushed plugin.upload_plugin commands that installed backdoors on connected WordPress sites after a weekend breach of teamupdraft.com. Patchstack counted 99 backdoor names in an 18-hour window. UpdraftPlus 1.26.13 and 2.26.13 revoke many keys, but responders still have to check every site by hand.

Noah Park, ResponseNew York6 min read

NEW YORK - TeamUpdraft, the company behind the UpdraftPlus WordPress backup plugin, has confirmed that an attacker who broke into teamupdraft.com over the weekend of Oct. 17 and 18 obtained connection keys for its UpdraftCentral Cloud remote-management service and used them to push plugins onto customer sites. The plugins were backdoors. Patchstack, which monitors WordPress sites at scale, counted 99 distinct backdoor names between 15:32 UTC on Oct. 18 and 09:23 UTC on Oct. 19.

This is not a bug in the plugin. The commands were correctly encrypted and signed with genuine dashboard private keys, so every check on the site passed. Nethemba, the Slovak security firm that first published a technical breakdown after three of its own sites were hit, wrote that the fault was not on the customers' side. Self-hosted UpdraftCentral dashboards were not affected, TeamUpdraft said. Backups stored on customers' own remote storage were not affected either. The UpdraftPlus plugin downloads themselves were clean.

UpdraftPlus has more than 4 million active installations, according to wordpress.org figures cited by both Nethemba and Patchstack. The UpdraftCentral client ships inside every free and premium copy. A site only accepts remote commands once it holds a connection key. That key can be created without the owner noticing: when someone logs into a teamupdraft.com account inside the plugin, the checkbox that reads "Add this website to UpdraftCentral" is ticked by default.

How the keys became a takeover channel

UpdraftCentral works by generating an RSA key pair on the site and storing the dashboard's public key there. The dashboard's private key never leaves the UpdraftCentral Cloud service. From then on the site will execute any command signed with that private key, with the rights of the WordPress user who created the connection, and without a second confirmation.

TeamUpdraft security-incident notice update of Oct. 21, 2026, 10:23 BST, stating that the attacker used a compromised key, that UpdraftPlus 1.26.13 and 2.26.13 automatically disconnect sites from UpdraftCentral by revoking connection keys, and that customers should check for unexpected plugins and admin accounts.
Screenshot: TeamUpdraft, security-incident notice update of Oct. 21, 2026 (fair use).

Nethemba's analysis of its own logs showed the pattern. From IP address 43.250.53.42, with the User-Agent WordPress/6.4; class-udrpc.php, the attacker first sent a probe addressed to a non-existent key, probe.central.updraftplus.com. A site that answers that probe has revealed that it accepts UpdraftCentral commands. The next command went to the real key and carried plugin.upload_plugin. On two of Nethemba's three sites the command succeeded and WordPress installed and activated an unknown plugin through its normal installer. On the third the key belonged to a user who no longer had install_plugins rights, and the push failed.

TeamUpdraft said in its own notice that it closed the access route, signed out every account, replaced UpdraftVault and UpdraftClone credentials, released UpdraftPlus 1.26.13 (free) and 2.26.13 (Premium) to revoke connection keys, reported the matter to the UK Information Commissioner's Office and the police, and brought in an external security firm. It said the speed of the follow-on exploits and the initially faulty backdoors suggested the attackers used AI to accelerate the attack. It also said there was currently no evidence the attacker still had access to teamupdraft.com.

Nethemba timeline table for sites A, B and C listing probe and plugin-installation times in CEST, the attacker IP 43.250.53.42, the User-Agent WordPress/6.4; class-udrpc.php, and the backdoors Load Stack 35C and Text Gantry Eb0.
Screenshot: Nethemba, timeline of probes and plugin installations on three WordPress sites, Oct 19, 2026 (fair use).

What the backdoors did

The first wave of plugins, Nethemba wrote, was meant to create a disguised administrator when given a secret URL token: an Editor account with manage_options and install_plugins added separately, so a routine review of administrators would miss it. Login happened by setting a cookie directly, which bypasses the login form, two-factor authentication and login-attempt limits. Early samples carried a coding error that crashed the site with HTTP 500 on every uncached request, which is how Nethemba noticed within minutes. Later samples worked. One variant hid itself from the plugin list. Another logged the attacker in as an existing administrator and left no new account behind.

Patchstack's telemetry matched that picture and widened it. It saw two source addresses active at once, 43.250.53.42 and an IPv6 address, and 99 distinct plugin names. One name, Site Health Cache, was reused; the rest were randomised two- or three-word combinations. The description line "Small maintenance toolkit: keeps option storage tidy." was shared across the first-variant samples and is the reliable file-level indicator Patchstack published.

Patchstack indicators of compromise listing the plugin description Small maintenance toolkit: keeps option storage tidy., the attacker User-Agent WordPress/6.4; class-udrpc.php, and a block of observed backdoor plugin names including Site Health Cache.
Screenshot: Patchstack, indicators of compromise for the UpdraftCentral key-compromise campaign, Oct 19, 2026 (fair use).

Nethemba kept updating through Oct. 22. It reported that the attacker continued to send UpdraftCentral commands from 43.250.53.42 after 1.26.13 shipped, that version 1.26.12 / 2.26.12 did not delete any keys because of a bug, and that even 1.26.13 deletes only keys created before 12:07 UTC on Oct. 18, leaving keys created later that day to be removed by hand. Keys do not expire: Nethemba said keys from November 2025 still worked in October 2026.

What responders should do now

  • On every WordPress site that runs UpdraftPlus, free or premium, check for an UpdraftCentral key even if no one remembers enabling UpdraftCentral. In the admin: Settings, UpdraftPlus Backups, Advanced Tools, UpdraftCentral. Or run wp option get updraft_central_localkeys.
  • Delete every key on the site. Removing the site from the UpdraftCentral dashboard is not enough; the key that matters lives on the site. Backups keep working after deletion.
  • Update to UpdraftPlus 1.26.13 or 2.26.13 or later. Do not stop at 1.26.12 / 2.26.12. After updating, still confirm that no key remains, and delete by hand any key created on Oct. 18 between 12:07 and 21:00 UTC.
  • Inspect Plugins, including Must-Use plugins, for anything you did not install. Look for the description Small maintenance toolkit: keeps option storage tidy. Nethemba publishes a read-only checking script that also catches renamed and hidden variants by their code.
  • Review Users for unexpected administrators and for Editor accounts that hold manage_options or install_plugins. Change every administrator password, end sessions and enable two-factor authentication.
  • Change the teamupdraft.com account password by typing the address into the browser. Reset two-factor authentication on that account. If UpdraftPlus Premium kept the account password in the database option updraftplus-addons_options, remove it and treat it as exposed.
  • If a backdoor, an unexpected admin or a matching trigger request appears in access logs, treat the site as fully compromised: restore from a backup taken before Oct. 17, compare files to a clean install and rotate every credential that the site could reach, including remote-storage keys.
  • Warn operators that follow-on phishing claiming to be from TeamUpdraft is likely. TeamUpdraft says it will never ask for passwords or keys by email.

Sources:


Noah Park covers incident response, containment, and blue-team operations for SOCtember from New York.

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