Nextcloud Bug Bounty Program

About our project

Nextcloud is an open-source platform that enables users and organizations to host their own cloud storage and collaboration services. It offers functionalities similar to commercial solutions like Google Drive or Dropbox but gives users full control over their data by allowing it to be stored on private servers.

With Nextcloud, users can synchronize and share files, manage calendars and contacts, collaborate on documents in real time, and even host video calls — all within a secure and customizable environment.

Its strong focus on privacy, extensibility, and compliance makes it a popular choice for businesses, institutions, and individuals who value data sovereignty.

We're inviting researchers all over the globe to take a look at Nextcloud and bring its security to the next level. If you're interested in learning how we handle security you can read more about it on our dedicated security page.

About the scope

This program is limited to a specific list of assets, reports about out of scope assets won't be eligible for reward. Please reproduce the issue locally with an up to date version before reporting.

In order to know how to set up a development environment, check our developer manual.

About our threat model

You may find our threat model documentation here.
Please make sure that your reports are aligned with it, otherwise it won't be eligible for a reward.

Program rules

Reports content

To be eligible, your reports must include the hereafter information:

• General description of the issue
• Details about the impacted function and specific conditions to be met, including the vulnerable code snippet
• Impacted version
• A step by step proof of concept allowing to reliably reproduce the issue, including network exploitation
• Recommendations and fix suggestions

A detailed template will be provided automatically when submitting a report, please stick to it. This will help us ensure a smooth and swift processing of your reports.

Mind that reports that do not follow the template’s guidelines won’t be eligible for reward. Abuse may lead to further sanctions (e.g. spamming or repeated submission of invalid reports).

XSS requirements

For an XSS report to be eligible a basic proof-of-concept is not considered enough to be eligible. A clear and actionable impact resulting from the XSS has to given, example given:

• Privilege escalation or other bypassing of existing security controls
• Extracting PII or authentication details by sending them to an external server
• Performing requests as another user, including but not limited to: upload a file or changing settings

Testing Policy, Responsible Disclosure

Please adhere to the following rules while performing research on this program:

• Denial of service (DoS) attacks on our applications, servers, networks or infrastructure are strictly forbidden
• All reports must be validated manually, submission from automated tools won't be considered and may lead to sanctions (code analysis tools, AI, …)
• Targeting other users' instances is forbidden, only test against your own
• DO NOT include Personally Identifiable Information (PII) in your report and please REDACT/OBFUSCATE the PII that is part of your PoC (screenshot, server response, JSON file, etc.) as much as possible.
• Same with secrets, keys and credentials
• No vulnerability disclosure, full, partial or otherwise, is allowed without prior agreement from us
• Please avoid submitting security issues on our repositories before reporting it to this program, your report might be considered as a duplicate if a related submission already exists on our repositories
• The following topics won’t be considered as a valid finding eligible for reward nonetheless, you’re welcome to suggest improvements about it through our repositories but not our bug bounty program:
  • Code improvements/code quality issues without security impact
  • Insecure default/basic configurations
  • Mistakes or lack of precision in our documentation

Large Language Model (LLM) usage

• If you use large language models (LLMs), please disclose how you've used them, and carefully review and edit its output before you send it to us. Please double-check that your reproduction steps actually work and that all the information you've included in the report is valid and correct.
• Don't leak the contents of your report up front to any SaaS solutions, such as AI services like ChatGPT, search engines, browser plugins, or translation engines. If you use services, such as large language models, only use services that run locally on your own hardware to ensure our security information does not leak to the outside world.
• As a reminder, all reports must be validated manually, submission from automated tools won't be considered and may lead to sanctions.

Additional Information

What we're especially looking after:

• Bugs within Nextcloud server and apps supported by Nextcloud GmbH (Note: see Scope list for all qualifying and packaged components. Third-party apps from the App Store are not part of our bounty program.)
• Bugs within the mobile iOS and Android sync clients
• Bugs within the desktop clients for Mac, Windows, and Linux

We believe in transparency about our security, so any valid vulnerabilities discovered are always publicly disclosed after a grace period.

Reward

Eligibility

We are happy to thank everyone who submits valid reports which help us improve the security, however only those that meet the following eligibility requirements may receive a monetary reward:

• You must be the first reporter of a vulnerability
• You must not break any of the program policy rules listed above
• You must not be a former or current employee nor a maintainer of our project or one of its contractors
• The vulnerability must be a qualifying vulnerability
• The report must contain the following elements:
  • Clear textual description of the vulnerability, how it can be exploited, the security impact it has on the application, its users and the company, and remediation advice on fixing the vulnerability
  • Proof of exploitation: screenshots demonstrating the exploit was performed, and showing the final impact
  • Provide complete steps with the necessary information to reproduce the exploit, including (if necessary) code snippets, payloads, commands etc
• Identical vulnerabilities present in different versions will be considered as a single issue/will warrant a single reward
• Multiple vulnerabilities caused by one underlying issue will be considered as a single issue/will warrant a single reward

Reward amounts are based on:

• Reward grid of the report's scope
• CVSS scoring and actual business impact of the vulnerability upon performing risk analysis