ERI File Library (≤ 1.1.0) — Missing Authorization Allows Unauthenticated Protected File Download (CVE-2025-12041)

Author: Hong Kong Security Expert

Published: 2025-10-31

Introduction

On 31 October 2025 a Broken Access Control vulnerability affecting the ERI File Library plugin (versions ≤ 1.1.0, fixed in 1.1.1) was published as CVE-2025-12041. The flaw allows unauthenticated users to download files intended to be protected by the plugin due to missing or incorrect authorization checks.

This advisory gives concise, pragmatic guidance for site owners and administrators: what the issue is, how attackers typically abuse it (conceptually), detection methods, immediate mitigations you can apply now, and longer-term hardening steps. No exploit code is provided.

Executive summary (what you need to know)

• Vulnerability: Broken Access Control — missing authorization check for file downloads.
• Affected versions: ERI File Library ≤ 1.1.0
• Fixed in: 1.1.1
• CVE: CVE-2025-12041
• Privilege required: Unauthenticated (no login required)
• Risk: Confidential/protected files may be downloaded by anyone who can reach the plugin’s download endpoint.
• Immediate action: Update the plugin to 1.1.1 or later. If you cannot update immediately, apply temporary access controls at the webserver or edge level, or restrict the plugin path until you can patch.

What the vulnerability actually is (plain language)

File-management plugins must verify two things before serving a protected file:

1. Authentication — is the requestor logged in?
2. Authorization — does the requestor have permission to access the requested file?

This vulnerability is a missing-authorization issue: the plugin exposes a download endpoint that serves files without verifying that the requester has rights to that specific file. Anonymous visitors or automated crawlers can thus enumerate or directly download files that were intended to be private (customer documents, invoices, private images, attachments, etc.).

Although this is not remote code execution or SQL injection, the immediate impact is data exposure. Exposed files can include secrets or configuration that enable follow-on attacks.

How an attacker would typically abuse this (conceptual)

• Locate the plugin’s download endpoint (common patterns include plugin directories or AJAX endpoints used by the plugin).
• Craft requests referencing file identifiers: IDs, tokens, file names, or paths.
• Because authorization is not enforced, the server returns file content regardless of authentication.
• The attacker can download protected files, possibly in bulk, by enumerating predictable IDs or guessing paths.

No exploit code is provided here; the focus is detection and remediation.

Exploitability and impact analysis

• Exploitability: High for data access — straightforward if file identifiers are predictable or discovery is possible.
• Impact: Confidentiality breach. Exposed files may include PII, financial documents, private images, or secrets (API keys, environment files) that increase downstream risk.
• CVSS: Published CVSS baseline: 5.3. Site-specific risk can be higher depending on stored data.

Detection and indicators of compromise (what to look for)

Check these sources to determine whether the vulnerability has been abused on your site:

1. Webserver access logs (Apache, Nginx)

• Frequent GET requests to plugin paths, e.g. paths containing /wp-content/plugins/eri-file-library/ or query parameters indicating downloads (id, file, token, file_id, download).
• Large numbers of 200 responses for download endpoint requests from previously anonymous IPs.
• Requests for sensitive extensions (.pdf, .xls, .env, .pem, .zip) from unauthenticated sources.

Example grep patterns:

grep -E "eri-file-library|eri_file_library|file_library" /var/log/nginx/access.log

grep -E "\.pdf|\.xls|\.xlsx|\.csv|\.env|\.sql|\.pem|\.zip" /var/log/nginx/access.log | grep -i "eri-file-library"

2. Application logs

• Plugin logs showing download requests without an associated user or showing session anomalies.
• Unusual spikes in admin-ajax requests including file identifiers.

3. Hosting control panel / storage logs

• Object storage access logs (S3, Spaces) showing direct downloads mapped to plugin-managed objects.
• File system timestamps: reads of protected files at times corresponding to suspicious IPs.

4. Analytics and SIEM

• Download endpoint events from new or suspicious IPs/geographies; spikes in traffic to plugin endpoints.

5. User reports

• Users reporting leaked files or receiving unexpected access notifications.

If any indicators appear, preserve logs and follow the incident response steps below.

Immediate mitigation steps (short term)

If you cannot update ERI File Library immediately, apply one or more temporary mitigations to block unauthenticated access:

1. Update the plugin. The most reliable fix is to install ERI File Library 1.1.1 or later on all sites.
2. Block or restrict plugin endpoints at the webserver or edge. Deny public access to the plugin folder or download endpoints unless authenticated. Use IP allowlists, Basic Auth, or block public access and allow only admin IPs until patched.
3. Require WordPress login cookie for downloads (temporary WAF/webserver rule). Block requests lacking a WordPress login cookie (cookies beginning with wordpress_logged_in_). This reduces anonymous exploitation but is not a full authorization check.
4. Move protected files out of the webroot. If plugin settings allow, relocate private assets outside public web directories so they cannot be fetched by simple HTTP GETs.
5. Disable the plugin while you patch. If the plugin is non-critical and mitigation is not possible, deactivate it until patched.
6. Limit file types. Remove or relocate extremely sensitive files (.env, .sql, .pem) that may have been uploaded by mistake.

Virtual patching and WAF rules — example signatures

Use these example rules as temporary virtual patches on your WAF or webserver. Test rules in monitoring mode before blocking to avoid false positives. Adapt paths and argument names to your environment.

ModSecurity (example)

# Block unauthenticated access to ERI File Library download endpoints
SecRule REQUEST_URI "@rx /wp-content/plugins/eri-file-library/|/wp-admin/admin-ajax.php" \
  "phase:1,chain,deny,log,status:403,msg:'Blocked unauth file download attempt (ERI File Library)'"
  SecRule ARGS_NAMES|ARGS "@rx (file|file_id|id|download|token)" "chain"
  SecRule REQUEST_HEADERS:Cookie "!@rx wordpress_logged_in_"

Explanation:

• Match likely plugin URIs or admin-ajax; look for parameters used for downloads; deny when no WordPress login cookie is present.

Nginx (location block) — simple blocking by path

# Deny access to plugin download endpoint (temporary)
location ~* /wp-content/plugins/eri-file-library/.*download.* {
    return 403;
}

# Or deny direct access to plugin's download script
location = /wp-content/plugins/eri-file-library/download.php {
    return 403;
}

Nginx + Lua (cookie-based check)

access_by_lua_block {
  local uri = ngx.var.request_uri
  if uri:find("eri%-file%-library") or uri:find("download") then
    local cookie = ngx.var.http_cookie or ""
    if not cookie:find("wordpress_logged_in_") then
      ngx.log(ngx.ERR, "Blocked unauthenticated access to ERI File Library download endpoint")
      return ngx.exit(403)
    end
  end
}

Notes:

• Cookie checks enforce presence of an authenticated session, not per-file authorization.
• If your environment cannot safely use these, prefer disabling the plugin or restricting access by IP ranges.

Long-term mitigation and secure design recommendations

Use this incident as an opportunity to strengthen how private assets are served and managed.

1. Enforce proper server-side authorization. Every file download flow must verify both authentication and fine-grained authorization: ensure the current user has rights to access the specific file (owner or role-based).
2. Use non-guessable tokens. For temporary URLs, ensure tokens are long, random, single-use or time-limited.
3. Store sensitive files outside the web root. Serve files through a controlled script that enforces permission checks, using X-Accel-Redirect or X-Sendfile patterns where the application authorises then instructs the server to deliver the file.
4. Audit plugin permissions and file upload code. Confirm file listing functions don’t leak identifiers or directory indexes.
5. Apply least-privilege. Administrative operations should require appropriate capabilities; avoid overly broad roles that can enumerate or download files.
6. Maintain update discipline. Automate or schedule plugin updates; apply critical security fixes promptly.

Incident response checklist (if you detect suspicious downloads)

1. Preserve logs. Archive relevant access and error logs to an offline location for forensic analysis.
2. Patch immediately. Update ERI File Library to 1.1.1 or later. If not possible, disable the plugin or apply temporary access controls.
3. Identify exposed files. Use logs to enumerate which files were served and cross-check with inventory to find sensitive items.
4. Assess impact. Determine whether exposed files contain PII, credentials, or regulated data and classify severity.
5. Notify affected parties. If regulated data or PII was exposed, follow legal and contractual notification obligations.
6. Rotate keys. If files contain API keys, tokens or credentials, rotate them immediately.
7. Scan for follow-on activity. Perform malware scans and integrity checks to ensure no further compromise occurred.
8. Harden and monitor. Apply long-term mitigations and increase monitoring for suspicious activity.
9. Post-incident review. Document root cause and update procedures to prevent recurrence.

Recommended log-search queries (practical)

Use these quick searches on typical Linux hosts to find suspicious download activity. Adjust patterns as needed.

# Find GET requests with 'download' or 'file' in query
grep -iE "download|file|file_id|fileid|token" /var/log/nginx/access.log | grep -i "eri-file-library"

# Find requests for sensitive extensions via plugin paths
grep -iE "eri-file-library" /var/log/nginx/access.log | grep -E "\.pdf|\.xls|\.xlsx|\.csv|\.env|\.sql|\.pem|\.zip"

# Count unique IPs requesting downloads in the last 7 days
grep -i "eri-file-library" /var/log/nginx/access.log | awk '{print $1}' | sort | uniq -c | sort -nr | head -n 50

# Identify large responses (possible file downloads)
awk '$10 ~ /^[0-9]+$/ && $10 > 1000000 {print $0}' /var/log/nginx/access.log | grep "eri-file-library"

Edge protection and detection heuristics (conceptual)

Managed edge protections and WAFs can reduce exposure by applying virtual patches and detection rules — but they are complements, not substitutes, for correct in-app authorization. Example heuristics to consider:

• Flag requests to plugin download endpoints when no wordpress_logged_in_ cookie is present and query parameters indicate file IDs, and the response size suggests a file delivery (>50KB).
• Rate-limit repeated requests for different file IDs from a single IP (e.g., >50 distinct file downloads per hour).
• Alert on sequential numeric IDs returning many 200 responses (enumeration pattern).
• Detect token brute-force attempts by counting repeated token guesses from single IPs.

Start detection in monitoring mode to tune rules and reduce false positives before blocking.

Hardening checklist you should perform now

• Update ERI File Library to 1.1.1 or later on every site.
• Review sensitive files stored in plugin-controlled areas and relocate them if needed.
• Audit plugin code or request vendor confirmation to ensure authorization checks are present for any file-serving controller.
• Add temporary server or WAF rules to block unauthenticated access to plugin endpoints until patched.
• Scan the site for exposed PII or secrets and rotate any exposed credentials.
• Maintain backups and enable file integrity monitoring.
• Configure alerts for unusual spikes in download activity.

Why you should act quickly (risk reminders)

• The vulnerability requires no authentication — any visitor who can reach the endpoint may access files.
• Attackers routinely scan for plugin endpoints and attempt automated downloads; a small window can lead to bulk leakage.
• Exposed files may contain secrets enabling further compromise; credential rotation is often necessary after exposure.

Final thoughts — practical steps for site owners and developers

For site owners:

• Treat private files as high-value assets. Even a convenience plugin can leak data if authorization is overlooked.
• Keep plugins updated and monitor access to plugin-specific endpoints.
• Use layered defence: correct in-code authorization, hosting configuration (files outside webroot), and edge protections where appropriate.

For plugin developers:

• Validate both authentication and authorization for every file-serving action.
• Use non-guessable identifiers and time-limited download tokens.
• Incorporate permission checks into automated tests and threat modelling.
• Provide clear changelogs and security notices; patch and communicate fixes promptly.

Assistance

If you need professional help assessing exposure, hardening servers, or implementing temporary virtual patches, engage a qualified security consultant or your hosting provider’s security team. Preserve evidence and act quickly to update or isolate affected systems.

Stay vigilant,

Hong Kong Security Expert