CVE-2026-6555: ProSolution WP Client Arbitrary File Upload Critical RCE
The National Vulnerability Database reports a critical arbitrary file upload vulnerability, CVE-2026-6555, in the ProSolution WP Client plugin for WordPress, affecting all versions up to and including 2.0.0. This flaw, rated 9.8 CVSS, stems from a validation mismatch during file uploads. While the first file in an upload array undergoes proper extension and MIME type validation, subsequent files are not checked.
This oversight allows unauthenticated attackers to bypass security measures. By submitting a legitimate file followed by a malicious PHP file, attackers can upload arbitrary code to a web-accessible directory. This effectively grants them remote code execution (RCE) capabilities, enabling full control over the compromised WordPress site.
For defenders, this is a clear and present danger. An unauthenticated RCE is the holy grail for attackers. Organizations running WordPress sites with this plugin must prioritize patching or removal immediately. The ease of exploitation, coupled with the critical impact, makes this a prime target for automated attacks.
What This Means For You
- If your organization uses the ProSolution WP Client plugin on any WordPress installation, you are exposed to unauthenticated remote code execution. Immediately identify all instances of this plugin, disable it, and remove it until a patch is available. Conduct a forensic review of your web server logs for any suspicious file uploads or PHP execution attempts if you were running affected versions.
Related ATT&CK Techniques
🛡️ Detection Rules
3 rules · 6 SIEM formats3 detection rules auto-generated for this incident, mapped to MITRE ATT&CK. Sigma YAML is free — export to any SIEM format via the Intel Bot.
CVE-2026-6555: ProSolution WP Client Arbitrary File Upload
title: CVE-2026-6555: ProSolution WP Client Arbitrary File Upload
id: scw-2026-05-20-ai-1
status: experimental
level: critical
description: |
Detects the specific arbitrary file upload vulnerability in the ProSolution WP Client plugin (CVE-2026-6555). This rule looks for POST requests to the plugin's upload endpoint, which is a key indicator of exploitation. The vulnerability allows unauthenticated attackers to upload malicious PHP files, leading to RCE.
author: SCW Feed Engine (AI-generated)
date: 2026-05-20
references:
- https://shimiscyberworld.com/posts/nvd-CVE-2026-6555/
tags:
- attack.initial_access
- attack.t1190
logsource:
category: webserver
detection:
selection:
cs-uri|contains:
- '/wp-content/plugins/prosolution-wp-client/'
cs-method|exact:
- 'POST'
sc-status|exact:
- '200'
cs-uri-query|contains:
- 'action=upload'
condition: selection
falsepositives:
- Legitimate administrative activity
Source: Shimi's Cyber World · License & reuse
Indicators of Compromise
| ID | Type | Indicator |
|---|---|---|
| CVE-2026-6555 | RCE | ProSolution WP Client plugin for WordPress versions <= 2.0.0 |
| CVE-2026-6555 | Arbitrary File Upload | ProSolution WP Client plugin for WordPress versions <= 2.0.0 |
| CVE-2026-6555 | Code Injection | Malicious PHP file upload via array validation mismatch in ProSolution WP Client plugin |
Written by SCW Vulnerability Desk
Source & Attribution
| Source Platform | NVD |
| Channel | National Vulnerability Database |
| Published | May 20, 2026 at 05:16 UTC |
This content was AI-rewritten and enriched by Shimi's Cyber World based on the original source. All intellectual property rights remain with the original author.
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