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CVE-2026-59555: Unauthenticated Arbitrary File Deletion

CVE explainers 10 min read
SR
Security Research Desk Expert reviewed
Threat intelligence · Human-verified · Updated 2026-07-23
▲ Escalation ViewOne CVE, briefed at three altitudes — skim the Brief, weigh the Impact, or work the Runbook. The way a SOC actually reads it.
CISOBrief · 30-second brief

TL;DR - Critical unauthenticated file deletion flaw in Participants Database for WordPress. - Affects versions up to and including 2.7.8.3; update to 2.7.8.4 now. - No confirmed in-the-wild exploitation cited here, but urgency is high due to remote no-auth exposure.

1) Vulnerability at a Glance

Field Value
CVE ID CVE-2026-59555
CVSS v3.1 10.0 Critical
Attack vector Network
Auth required No
Patch available Yes
Affected product Participants Database WordPress plugin
Affected versions Up to and including 2.7.8.3
Fixed version 2.7.8.4
Weakness CWE-22
Impact Unauthenticated arbitrary file deletion

This vulnerability affects the WordPress plugin Participants Database by Roland Barker. According to the NVD record, all versions up to and including 2.7.8.3 are affected, and the issue is fixed in 2.7.8.4. The flaw is described as an unauthenticated arbitrary file deletion vulnerability, which means a remote attacker may be able to trigger deletion of files without logging in.

For defenders, the operational takeaway is straightforward: if this plugin is installed and the version is 2.7.8.3 or earlier, treat the host as exposed until upgraded. Because the vulnerability is remotely reachable and requires no authentication and no user interaction, it belongs in the highest-priority patch queue even though public exploitation has not been confirmed in the sources available here.

2) What Is This Vulnerability?

The vulnerability is categorized under CWE-22, which points to an improper limitation of a pathname to a restricted directory. In practical terms, this usually means attacker-controlled input influenced a file path used by the application, and the application failed to properly normalize, validate, or constrain that path before performing a file operation. In this case, the operation described is file deletion.

The NVD description is concise: “Unauthenticated Arbitrary File Deletion in Participants Database <= 2.7.8.3 versions.” That tells defenders three important things with high confidence: the issue is remotely reachable, no login is needed, and the impact is destructive. The available research also notes that the WordPress.org changelog for version 2.7.8.4 references a directory traversal vulnerability fix, which aligns with the CWE-22 classification.

Because the currently available source material does not provide a full code diff or vendor-authored root-cause write-up, defenders should avoid assuming a specific function name, endpoint, or parameter unless verified directly from source code or a vendor advisory. The safe working assumption is that some public-facing plugin functionality accepted a path-like input that could be abused to reach files outside an intended directory and delete them.

A pure file deletion issue may sound narrower than code execution, but it can still be severe. Deleting WordPress core files, plugin files, media assets, or configuration-related data can cause application outages, integrity loss, and in some cases contribute to follow-on compromise depending on what is removed and how the site recovers.

Technical Notes

A typical vulnerable pattern for this class of bug looks like:

$target = $_POST['file'];
unlink($base_dir . '/' . $target);

A safer pattern validates canonical paths before deletion:

$requested = realpath($base_dir . '/' . $user_input);
$allowed   = realpath($base_dir);

if ($requested !== false && str_starts_with($requested, $allowed . DIRECTORY_SEPARATOR)) {
    unlink($requested);
}
AnalystImpact · assess the risk

3) Who Is Affected?

The affected product is the Participants Database plugin for WordPress, package slug participants-database, authored by Roland Barker. The affected version range is specifically “up to and including 2.7.8.3”. The fixed version is 2.7.8.4.

If you run WordPress and this plugin is present on any public-facing site, that site should be considered affected unless you have verified the installed version is 2.7.8.4 or later. This includes production sites, staging systems exposed to the internet, and temporary migration or QA instances that often fall behind on plugin updates.

This issue is especially relevant to SMBs and smaller IT teams because WordPress plugin exposure is often broader than expected. Organizations may have multiple independently managed websites, legacy marketing sites, or forgotten subdomains with outdated plugins. A no-auth vulnerability in a plugin can be exploited without valid credentials, so traditional assumptions such as “admins use MFA” do not materially reduce risk here.

If you do not know whether the plugin is installed, check directly in WordPress admin, on disk, or via WP-CLI. In the absence of an inventory, defenders should assume any WordPress site using Participants Database and reporting 2.7.8.3 or earlier is vulnerable.

Technical Notes

Check the installed plugin version with WP-CLI:

wp plugin list --path=/var/www/html | grep participants-database

Or inspect plugin metadata on disk:

grep -E "Version:" /var/www/html/wp-content/plugins/participants-database/participants-database.php

4) CVSS Score Breakdown

NVD assigns CVSS v3.1 10.0 Critical with the vector:

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Each part of that vector matters operationally. AV:N means the vulnerability is exploitable over the network. AC:L means exploitation is considered low complexity. PR:N confirms no privileges are required, and UI:N means the attacker does not need to trick a user into clicking or approving anything.

The S:C component, changed scope, contributes to the severity because the impact may extend beyond the initially vulnerable component. The impact triad is marked C:H/I:H/A:H, which is unusually severe for a deletion bug and indicates the scorer judged the downstream effects on confidentiality, integrity, and availability to be substantial. That does not prove every deployment will experience all three impacts, but it does justify emergency handling.

For defenders, the score should not be read as an academic number. It means the issue is easy to target remotely and can plausibly produce broad business impact. Even without confirmed exploitation, a no-auth CVSS 10.0 WordPress plugin vulnerability should move ahead of lower-severity authenticated or local issues in most remediation queues.

5) Exploitation Status

Based on the available source material, there is no verified public proof of concept cited here, and there is no confirmed in-the-wild exploitation reported in the referenced data. The research note specifically indicates that CISA KEV does not list CVE-2026-59555 at the time of checking. That means there is no CISA-confirmed evidence of exploitation from the KEV catalog for this CVE as of 2026-07-23.

That said, defenders should not interpret “not on KEV” or “no PoC verified” as low risk. WordPress plugin vulnerabilities are often easy to operationalize once the affected code path is understood, and the combination of network reachable, no authentication, and low attack complexity makes this the kind of flaw that can move quickly from disclosure to opportunistic scanning.

So the clearest statement is: PoC status unknown from primary sources available here; no verified public PoC found in the referenced research. Active exploitation in the wild is not confirmed in the sources reviewed. In the absence of confirmed exploitation data, defenders should still assume rapid weaponization is possible and patch accordingly.

ResponderRunbook · act now

6) How to Detect It

Detection is challenging when a vendor advisory does not publish exact request indicators, parameters, or endpoint names. In this case, the available source material does not confirm the exact vulnerable endpoint or parameter. Defenders should therefore focus on a combination of version-based exposure identification, unexpected file deletion symptoms, and anomalous requests touching plugin functionality.

Start by identifying any site running Participants Database 2.7.8.3 or earlier. That is the highest-confidence detection step. Then look for sudden WordPress errors, missing plugin assets, broken themes, missing uploads, or unexplained application failures shortly before or after suspicious HTTP requests. Also review web server and WAF logs for unusual requests involving the plugin slug, path traversal markers, or deletion-oriented parameters.

Because concrete vendor IOC data is unavailable, detection content should be treated as heuristic rather than signature-perfect. Use it to triage and hunt, not as proof of compromise by itself.

Technical Notes

Example web log hunt for requests referencing the plugin and possible traversal attempts:

grep -Ei 'participants-database|(\.\./)|(%2e%2e%2f)|delete|unlink|file=' /var/log/nginx/access.log

Example Sigma-style idea for suspicious requests to WordPress involving traversal patterns:

title: Possible exploitation attempt against Participants Database
logsource:
  category: webserver
detection:
  selection1:
    cs-uri-query|contains:
      - "../"
      - "%2e%2e%2f"
      - "file="
  selection2:
    cs-uri-stem|contains:
      - "participants-database"
  condition: selection1 and selection2
level: high

Example Splunk search:

index=web (uri_path="*participants-database*" OR uri_query="*participants-database*")
| search uri_query="*../*" OR uri_query="*%2e%2e%2f*" OR uri_query="*file=*"
| stats count values(src_ip) values(http_method) values(status) by host uri_path uri_query

Operationally, also monitor for sudden filesystem changes under WordPress paths:

find /var/www/html -type f -mmin -120 | sort

And for application errors that may indicate deleted files:

grep -Ei 'No such file|failed to open stream|include\(|require\(' /var/log/php*-fpm.log /var/log/apache2/error.log /var/log/nginx/error.log

7) Mitigation and Patching

The primary mitigation is to upgrade Participants Database to version 2.7.8.4 or later. That is the fixed version identified in the available records. If the plugin is installed and the version is 2.7.8.3 or earlier, patching should be treated as urgent.

If you cannot patch immediately, reduce exposure while scheduling the update. Because the flaw is unauthenticated, temporary mitigations should focus on disabling the plugin, restricting public access to the site or affected functionality, and ensuring recent backups exist in case files have already been deleted. Keep in mind that these are compensating controls, not a substitute for the fixed version.

Where exact exploit mechanics are unknown, a conservative workaround is warranted. If the site does not critically depend on Participants Database, disabling the plugin until the update window may be the safest short-term choice. If the site is business-critical, consider putting it behind stricter WAF rules and monitoring while prioritizing upgrade completion.

Technical Notes

Upgrade with WP-CLI:

wp plugin update participants-database --path=/var/www/html

Verify the installed version after update:

wp plugin get participants-database --field=version --path=/var/www/html

If you need to temporarily disable the plugin:

wp plugin deactivate participants-database --path=/var/www/html

Manual filesystem workaround if WP-CLI is unavailable:

mv /var/www/html/wp-content/plugins/participants-database \
   /var/www/html/wp-content/plugins/participants-database.disabled

If emergency web server blocking is needed, restrict direct access to WordPress while you patch. Example Nginx maintenance-style restriction:

location / {
    allow 203.0.113.10;
    deny all;
}

After patching, inspect file integrity and restore missing files from known-good backups if needed. Because the issue involves deletion, post-patch recovery may matter as much as patch deployment itself.

8) References

The highest-confidence reference is the NVD record for CVE-2026-59555, which provides the vulnerability description, affected range, fixed version, CVSS vector, and CWE mapping. That record identifies the issue as an unauthenticated arbitrary file deletion vulnerability affecting Participants Database <= 2.7.8.3, fixed in 2.7.8.4.

The official WordPress.org plugin page is also relevant because it confirms the product identity, plugin slug, author, and current plugin version context. A Patchstack advisory URL is listed as a reference in the NVD record, but the exact low-level exploit details were not confirmed from source text available here. Where details remain unverified, defenders should rely on what is clearly supported: affected range, fixed version, vulnerability class, and urgency.

For further insights on vulnerabilities, consider reviewing our glossary on phishing and software supply chain attacks.

If you run WordPress at scale, add this CVE to your plugin exposure review immediately. Even without confirmed in-the-wild exploitation, CVE-2026-59555 has the characteristics of a vulnerability that should be remediated before routine maintenance items.

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Last verified: 2026-07-23

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