FOSSBilling is a free, open-source billing and client management system. Prior to version 0.8.1, downloadable product files are stored using a deterministic filename-derived path. When an administrator uploads a file for a downloadable product, FOSSBilling stores the file as md5(<original filename>) under the uploads directory. Because the stored path depends only on the client-supplied filename, two different downloadable products, or product/order files, uploaded with the same original filename will resolve to the same stored file path. A later upload can overwrite an earlier upload, causing customers or administrators downloading the earlier product to receive the later file instead. Version 0.8.1 patches the issue. Some workarounds are available. Restrict the servicedownloadable.manage permission to fully trusted administrators only. As an operational mitigation, ensure downloadable product files use unique filenames before upload. This reduces accidental collisions but does not fully address the underlying issue.

FOSSBilling is a free, open-source billing and client management system. In versions 0.5.3 through 0.7.2, the Guest serviceapikey/getinfo API endpoint is accessible without authentication. Any caller with a valid API key can retrieve all custom configuration parameters (custom fields) stored in the key's database record. These custom fields are populated by billing administrators and can contain business-sensitive data such as pricing tiers, feature flags, rate limits, expiry overrides, or access scope data. Version 0.8.0 patches the issue. Some workarounds are available. Administrators can avoid storing sensitive data in custom API key configuration fields, monitor API logs for suspicious calls to /api/guest/serviceapikey/getinfo, and/or disable the Serviceapikey module if not in active use.

FOSSBilling is a free, open-source billing and client management system. Versions 0.5.3 through 0.7.2 allow authenticated clients to both read and reset API key service secrets for orders that are no longer in an active state (e.g., suspended, canceled). The root cause is missing order-state validation in two client API endpoints, despite an isActive() helper already existing in the Serviceapikey module and the frontend UI correctly gating access on order.status == 'active'. Version 0.8.0 contains a fix. Some workarounds are available. If the Serviceapikey module is not needed, uninstall it to remove the affected endpoints. One may also use a reverse proxy or WAF to restrict access to /api/client/order/service and /api/client/serviceapikey/reset based on application-level order-state logic.

FOSSBilling is a free, open-source billing and client management system. Versions prior to 0.8.0 allow low-privileged staff accounts to perform unauthorized actions via admin API endpoints. The root cause is a combination of the canalwaysaccess module flag (which grants all staff access to certain modules) and insufficient permission checks or unsafe parameter handling on individual endpoints. Version 0.8.0 contains a fix. Some workarounds are available. Restrict staff accounts to only those who need access to sensitive settings and/or use a reverse proxy or WAF to restrict access to the affected endpoints to trusted IP addresses or higher-privilege roles.

FOSSBilling is a free, open-source billing and client management system. In versions 0.5.6 through 0.7.2, when the "Require Email Confirmation" setting is enabled, a logged-in client with an unverified email address (emailapproved = 0) can access all client-area pages (e.g. /client/balance, /client/order/list, /client/invoice) and read real account data, including wallet balances and transaction history. The API-side enforcement correctly restricts unverified clients to only profile-related endpoints, but the page-side enforcement is overly permissive, allowing any request whose path starts with /client. Version 0.8.0 contains a fix. No known workarounds that don't involve modifying the source code are available.

FOSSBilling is a free, open-source billing and client management system. Versions 0.6.0 through 0.7.2 have a stored cross-site scripting (XSS) vulnerability in the client-facing email history views of FOSSBilling. Email HTML content (contenthtml) is rendered into a JavaScript template literal using the |raw filter, bypassing all output escaping. An attacker with admin access can inject malicious JavaScript payloads into email content that execute in the browser of any client who views their email history. Version 0.8.0 contains a fix. Some workarounds are available. Restrict admin account access, audit email content in the database for suspicious payloads, and/or monitor client accounts for unusual activity.

FOSSBilling is a free, open-source billing and client management system. Prior to version 0.8.0, low-privileged staff accounts may read sensitive data via admin API endpoints that lack permission checks. While sibling write endpoints correctly enforce fine-grained permissions, the corresponding read endpoints have no authorization guards. Version 0.8.0 contains a fix. Some workarounds are available. Restrict staff accounts to only those who need access to sensitive data and/or use a reverse proxy or WAF to restrict access to the affected endpoints.

FOSSBilling is a free, open-source billing and client management system. Prior to version 0.8.0, the PayPalEmail payment adapter accepts PayPal IPN callbacks and credits the IPN-supplied amount (mcgross) to the client's balance without validating it against the invoice total. Combined with a $0.05 floating-point epsilon tolerance in the invoice credit-payment logic, this allows a client to underpay an invoice by up to $0.04 and still have it marked as fully paid. Version 0.8.0 patches the issue. There is no effective workaround without modifying the source code. Merchants using the PayPalEmail adapter should monitor IPN transactions for amounts that do not match their corresponding invoice totals, and manually review and refund suspicious payments.

FOSSBilling is a free, open-source billing and client management system. Prior to version 0.8.0, a race condition in the cart checkout flow allows an authenticated client to apply a promo code beyond its configured maximum uses. By sending concurrent checkout requests before any single request completes the usage increment, a client can obtain unlimited discounted or free orders from a single-use or limited-use promo code. Version 0.8.0 patches the issue. Some workarounds are available. Disable promo codes entirely until a patch is available or monitor the promo table for used values exceeding maxuses and manually review affected orders.

FOSSBilling is a free, open-source billing and client management system. Prior to version 0.8.0, an unauthenticated mass assignment vulnerability in the client self-registration endpoint allows any visitor to assign themselves to an arbitrary client group during sign-up. Because client groups can gate promo code eligibility, an attacker may apply group-restricted discount codes and receive unauthorized discounts. Version 0.8.0 contains a patch. As a workaround, administrators can either remove group restrictions from promo codes or disable client self-registration (Settings → Clients → Disable signup).

FOSSBilling is a free, open-source billing and client management system. Versions 0.6.0 through 0.7.2 have a SQL injection vulnerability in the Massmailer module filter functionality. An authenticated administrator can supply crafted filter values when updating a mass email message, causing untrusted input to be interpolated directly into SQL in the recipient selection query. Version 0.8.0 patches the issue. Some workarounds are available. Restrict administrator access to trusted users only, disable the Massmailer module if it is not required, audit existing records in the modmassmailer table for suspicious filter values, and/or review administrator activity related to Massmailer message updates.

FOSSBilling is a free, open-source billing and client management system. Versions 0.6.0 through 0.7.2 have an unauthenticated payment bypass vulnerability in FOSSBilling's IPN callback endpoint. When the Custom payment adapter is enabled, an attacker can mark any unpaid invoice as paid and credit the associated client account without making an actual payment, by sending a single crafted HTTP request. Version 0.8.0 patches the issue. Some workarounds are available. Disable the Custom payment gateway if not actively needed and/or restrict access to /ipn.php at the web server level (e.g., via IP allowlisting), noting that this may interfere with legitimate payment callback processing.

FOSSBilling is a free, open-source billing and client management system. Versions 0.7.2 and prior expose a guest API endpoint, /api/guest/staff/create, intended for initial administrator bootstrap. Due to a flawed admin-existence check, the endpoint remains usable after an administrator already exists. The flawed guard check uses iscountable() on a value that returns a ModelAdmin object or null rather than a countable type, causing the expression to always evaluate as true and bypass the intended protection. As a result, an attacker can reach the unprotected endpoint to create a new administrator account and immediately authenticate, gaining a fully privileged admin session even when an admin already exists. This issue has been fixed in version 0.8.0.

FOSSBilling is a free, open-source billing and client management system. In versions 0.7.2 and prior, the Servicecustom Client API's call method accepts an orderid parameter and fetches the associated order without verifying the authenticated client owns it, potentially exposing cross-client data through IDOR. An authenticated client can access any other client's custom service by guessing sequential order IDs. This can lead to a confidentiality breach — attackers can read client PII (name, email, phone, address, company details, VAT number) and service configuration data belonging to other clients. This issue has been fixed in version 0.8.0.

FOSSBilling is a free, open-source billing and client management system. In versions 0.7.2 and prior, a query-construction flaw in client list endpoints allowed authenticated clients to bypass tenant scoping and retrieve other clients’ data. Details In ServiceTransaction::getSearchQuery() and Order\Service::getSearchQuery(), OR-based search/action filters were appended without grouping, allowing SQL operator precedence to evaluate OR clauses independently of the enforced clientid constraint. Crafted requests could therefore return records and metadata belonging to other clients, including identifiers, amounts, status, timestamps, and related fields. This issue was fixed in version 0.8.0.

FOSSBilling is a billing and client management system that automates invoicing, payments, and communication for online service businesses. Versions 0.6.21 through 0.7.2 are vulnerable to IDOR through the support ticket creation workflow. By manipulating relid when reltype=order, an authenticated client can create a support ticket that references another client's order they do not own. The ticketCreateForClient() method accepted relid without verifying order ownership for non-upgrade tasks, allowing clients to link a new ticket to another client's order by crafting the request. No cron task automatically processes cancel/upgrade requests from ticket relations; staff action is required. This affects integrity and confidentiality: staff could be misled into acting on the wrong order (e.g., cancellation or upgrade requests). While there is no client-to-client order data exposure, order IDs may appear in ticket context. This issue has been fixed in version 0.8.0.

FOSSBilling is a free, open-source billing and client management system. Starting in version 0.5.4 and prior to version 0.8.0, an authorization bypass in the API role handling allows unauthenticated access to privileged /api/system/ endpoints. Because system resolves to the cron admin identity, attackers can invoke admin API methods without valid credentials, session, or CSRF token. Version 0.8.0 patches the issue. Some workarounds are available. Block external access to /api/system/ at reverse proxy/WAF, restrict API access by trusted source IPs only (api.allowedips), rotate all admin/client API tokens immediately, invalidate active sessions and reset high-privilege credentials, and/or review API request logs for suspicious /api/system/ access and treat as potential incident.

FOSSBilling is a free, open-source billing and client management system. Versions prior to 0.8.0 have a Server-Side Template Injection (SSTI) vulnerability in the template rendering system. Administrators with access to features that render Twig templates (email templates, mass mail campaigns, custom payment adapters, and the stringrender API endpoint) can inject arbitrary Twig expressions, leading to information disclosure and remote code execution. The vulnerability exists because Twig templates are rendered without a sandbox, allowing access to the full Twig environment, API context, and the application's dependency injection container. Version 0.8.0 patches the issue. Some workarounds are available. Audit existing email templates for suspicious Twig expressions, rotate all admin and client API tokens, and/or block external access to /api/system/ at reverse proxy/WAF to mitigate chaining with GHSA-78x5-c8gw-8279.

FOSSBilling is a free, open-source billing and client management system. Prior to version 0.8.0, the password reset confirmation endpoint /client/reset-password-confirm/:hash is handled by a non-API controller and is not covered by FOSSBilling's rate limiter, which only applies to /api/ routes. This allows an attacker to probe the endpoint for valid reset tokens without any per-IP request limiting, attempt counting, or lockout mechanism. The endpoint acts as an oracle, returning a distinguishable response for valid versus invalid tokens (HTTP 200 vs HTTP 302 redirect). An attacker can submit unlimited token guesses to the password reset confirmation endpoint with no throttling applied. However, practical exploitability is significantly mitigated by the current token generation, which uses hash('sha256', randombytes(32)), providing 256 bits of entropy. Tokens also expire after 15 minutes and are deleted after successful use. The same architectural gap applies to other controller-served auth routes, including /staff/email/:hash (admin password reset confirmation) and /client/confirm-email/:hash (email confirmation). Version 0.8.0 fixes the issue. Some workarounds are available. Configure a reverse proxy (e.g., Nginx, Apache, Cloudflare) to apply per-IP rate limiting to the /client/reset-password-confirm/ and /staff/email/ paths and/or use a WAF rule to limit request rates to these endpoints.

FOSSBilling is a free, open-source billing and client management system. Prior to version 0.8.0, the Redirect module does not validate the URL scheme of administrator-configured destination URLs before storing or issuing redirects. This allows arbitrary external URLs to be configured as redirect targets, creating an open redirect vulnerability exploitable for phishing attacks. Users following a legitimate FOSSBilling URL can be silently redirected to an attacker-controlled external site. The redirect is issued as a 301 (Moved Permanently) response, which browsers cache persistently, amplifying the impact. Exploitation requires administrator privileges to create or modify redirect entries, limiting practical attack scenarios to multi-admin environments or compromised admin accounts. Version 0.8.0 fixes the issue. Some workarounds are available. Restrict admin access to the Redirect module to trusted administrators only and/or audit existing redirect entries in the database (the extensionmeta table with extension = 'modredirect') for any unexpected or external target URLs.

FOSSBilling is a free, open-source billing and client management system. Versions prior to 0.8.0 leak the exact system version through asset cache buster parameters in HTML output, bypassing the hideversionpublic security setting. The FOSSBilling version is embedded in the query string of every <script> and <link> tag generated by the scripttag and stylesheettag Twig filters. This information is visible to all visitors — including unauthenticated guests — on every page, regardless of whether the hideversionpublic setting is enabled. The X-FOSSBilling-Version HTTP header and the guest.system.version API endpoint correctly honour the hideversionpublic setting, but the asset cache buster parameters were overlooked. Knowledge of the exact FOSSBilling version makes it significantly easier for malicious actors to identify known vulnerabilities applicable to a given installation and craft targeted exploits. While not a direct vulnerability on its own, it undermines the intended protection offered by the hideversionpublic setting and facilitates reconnaissance. Version 0.8.0 contains a patch. There is no practical workaround that removes the version from asset URLs without modifying source code.

Improper Input Validation in GitHub repository fossbilling/fossbilling prior to 0.5.4.

Cross-site Scripting (XSS) - Reflected in GitHub repository fossbilling/fossbilling prior to 0.5.4.

Improper Neutralization of Formula Elements in a CSV File in GitHub repository fossbilling/fossbilling prior to 0.5.3.

Unrestricted Upload of File with Dangerous Type in GitHub repository fossbilling/fossbilling prior to 0.5.3.

SQL Injection in GitHub repository fossbilling/fossbilling prior to 0.5.3.

Session Fixation in GitHub repository fossbilling/fossbilling prior to 0.5.1.

Code Injection in GitHub repository fossbilling/fossbilling prior to 0.5.1.

Business Logic Errors in GitHub repository fossbilling/fossbilling prior to 0.5.0.

Insufficient Granularity of Access Control in GitHub repository fossbilling/fossbilling prior to 0.5.0.