VulnerabilityPublished 4 May 2026

mckenziearts/livewire-markdown-editor · Livewire markdown editor: livewire-markdown-editor has arbitrary file upload that allows stored XSS via attachment

Affects mckenziearts/livewire-markdown-editorSource GCVE Database

CVSS 7.1 High : upgrade to 1.3 soon.

Data as of 27 Oct 2026, 00:07 UTC

CVSS 3.1 base score

7.1High

How severe the flaw is on the 0–10 CVSS scale.

Patch: Available – fixed in 1.3

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: Low
Integrity: High
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

What to do

Upgrade mckenziearts/livewire-markdown-editor to 1.3.

Affected software

Product	Affected	Fixed in
Packagistmckenziearts/livewire-markdown-editor	Affected <1.3	Fixed in 1.3

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Description

### Impact All versions of `mckenziearts/livewire-markdown-editor` prior to **v1.3** contain a critical arbitrary file upload vulnerability in the `MarkdownEditor::updatedAttachments()` Livewire handler. The handler calls `$file->store()` with no server-side validation of MIME type, extension, or file content. Any authenticated user with access to a page embedding `<livewire:markdown-editor>` can upload files of any type (`.html`, `.svg`, `.js`, `.php`, `.exe`, etc.) to the disk configured by `livewire-markdown-editor.disk`. When that disk is a public cloud bucket (S3, DigitalOcean Spaces, Cloudflare R2, Scaleway Object Storage — the common configuration when `FILESYSTEM_DISK` points to such a disk), uploaded files are served publicly with a guessed `Content-Type` header. The consequences include: - **Stored XSS** on the storage domain via uploaded `.html` or `.svg` files - **Phishing page hosting** on the application's own storage domain (trust laundering) - **Malware distribution** from a domain users associate with the application - **Markdown injection** in the editor output via crafted filenames (the client-supplied `getClientOriginalName()` value was inserted verbatim into the markdown) A real-world exploitation of this vulnerability was observed in production on a community platform using this package. ### Patches Upgrade to **v1.3** or later. ### Workarounds If developers cannot upgrade immediately, disable the upload UI on every instance of the editor by passing `:show-upload="false"`: ```blade <livewire:markdown-editor wire:model="content" :show-upload="false" /> ``` This hides the file input and prevents the vulnerable code path from being reached. ### Resources - Patch commit: https://github.com/mckenziearts/livewire-markdown-editor/pull/12 - Release: https://github.com/mckenziearts/livewire-markdown-editor/releases/tag/v1.3 - CWE-434: https://cwe.mitre.org/data/definitions/434.html - CWE-79: https://cwe.mitre.org/data/definitions/79.html

CWE-434Unrestricted Upload of File with Dangerous Type (opens in a new tab)
Base weaknessLikelihood of exploit: MediumCWE Top 25 (2025): #12OWASP Top 10 A06:2025: Insecure Design (opens in a new tab)
The product allows the upload or transfer of dangerous file types that are automatically processed within its environment.
Architecture and Design
Generate a new, unique filename for an uploaded file instead of using the user-supplied filename, so that no external input is used at all.
Architecture and Design · Enforcement by Conversion
When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs.
Architecture and Design
Consider storing the uploaded files outside of the web document root entirely. Then, use other mechanisms to deliver the files dynamically.
OWASP Cheat Sheets
Server Side Request Forgery Prevention (opens in a new tab)
Web Service Security (opens in a new tab)
Third Party Javascript Management (opens in a new tab)
File Upload (opens in a new tab)
Secure Design Principles (opens in a new tab)
OWASP ASVS 4.0.3
V12.5.2 (opens in a new tab)
V13.1.5 (opens in a new tab)
V12.2.1 (opens in a new tab)
Attack patterns
Accessing Functionality Not Properly Constrained by ACLs (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #1OWASP Top 10 A05:2025: Injection (opens in a new tab)
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Implementation · Architecture and Design
Understand the context in which your data will be used and the encoding that will be expected. This is especially important when transmitting data between different components, or when generating outputs that can contain multiple encodings at the same time, such as web pages or multi-part mail messages.
Architecture and Design · Implementation · Attack Surface Reduction
Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide…
OWASP Cheat Sheets
Cross Site Scripting Prevention (opens in a new tab)
DOM based XSS Prevention (opens in a new tab)
Injection Prevention (opens in a new tab)
Abuse Case (opens in a new tab)
Deserialization (opens in a new tab)
OWASP ASVS 4.0.3
V5.3.3 (opens in a new tab)
V1.5.1 (opens in a new tab)
Attack patterns
XSS Using MIME Type Mismatch (opens in a new tab)
DOM-Based XSS (opens in a new tab)
Reflected XSS (opens in a new tab)
Stored XSS (opens in a new tab)
Cross-Site Scripting (XSS) (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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What to do

Affected software

Description

WeaknessesCWE-434, CWE-79

Technical details

References

Community reviews

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