When pretix is used as the identity provider in a Single-Sign-On (SSO) setup for customer accounts, the system did not properly validate the responsetype requested in an authorization request against the configured grant type of the SSO client. This means that if an SSO client was configured to only allow the code response type, which requires knowledge of the client secret to use and would wrongfully send a response type like idtoken, it would receive back a valid token. Exploiting this requires the attacker to run JavaScript on the page specified by redirecturi, which must be from a list specified in the client configuration.

We found a chain of combining multiple weaknesses in the product that could allow an attacker to become any user in the backend and access any data:

The payment integration plugins Stripe (included in the core system), pretix-mollie, pretix-oppwa, pretix-bitpay, pretix-payone, pretix-secuconnect, pretix-sofort, and pretix-saferpay contain a code path that is intended for the transport of session parameters from a tab with isolated cookies (e.g. in the pretix widget) to a new tab. For this purpose, a set of session parameters is cryptographically signed and then passed to the new tab as a URL parameter. The plugins perform no further validation of the session parameters, other than the cryptographic signature being valid. This is fixed with the releases issued today by strictly validating that no session parameters outside of the scope of the respective plugin may be set.

An unrelated feature in the core system is used to generate redirect links that obfuscate any Referer headers for outgoing links to prevent leakage of secrets in URLs. This redirect page also requires cryptographically signed parameters. Unfortunately, it uses the same key and salt for the signature as the previously mentioned feature in the payment integration plugins. A motivated attacker with access to at least one event in the backend can trick the system into cryptographically signing arbitrary content using specially crafted links. In combination with the previous issue, the attacker could use this to set and modify arbitrary parameters on their user session by injecting the signed parameters into the feature of the payment providers. This is fixed with the releases issued today by using different salts for the signature for each plugin and feature.

A third, unrelated feature in the core system is used for admin users to act on behalf of another user, mostly for debugging purposes. With being able to insert arbitrary parameters into a session, an attacker can abuse this feature to change their session from their actual user to any user in the system by guessing a valid user ID. This is fixed with the release today by requiring unguessable information to be contained in the session of the user to switch to.

Malicious HTML content could be injected into the email address of an order, which pretix showed without sanitization on the confirmation page for individual tickets in that order.

Malicious HTML content could be injected into the content of a page in the pretix-pages plugin.

Malicious HTML content could be injected into the content rendered by the pretix-digital plugin.

When creating an export through the pretix API, API clients are returned an UUID value for their export job (a long, random string like 35742818-c375-4d15-839f-d49aecce94d6). Using this UUID, the API client can then request the actual file for download. The same kind of UUID is used in other places in pretix when temporary files are generated for internal use or download.

One remaining API endpoint, however, wrongfully did not verify if the UUID used for download actually belongs to a file that is supposed to be downloadable and belongs to the correct user. In reality, this is hard to exploit because an attacker would need to have access to a valid UUID for the file they desire which is unlikely to happen without a separate security problem giving them access to logs etc.

A new API endpoint introduced in pretix 2025 that is supposed to return all check-in events of a specific event in fact returns all check-in events belonging to the respective organizer. This allows an API consumer to access information for all other events under the same organizer, even those they should not have access to.

These records contain information on the time and result of every ticket scan as well as the ID of the matched ticket. Example:

{ "id": 123, "successful": true, "errorreason": null, "errorexplanation": null, "position": 321, "datetime": "2020-08-23T09:00:00+02:00", "list": 456, "created": "2020-08-23T09:00:00+02:00", "autocheckedin": false, "gate": null, "device": 1, "deviceid": 1, "type": "entry" }

An unauthorized user usually has no way to match these IDs (position) back to individual people.

Emails sent by pretix can utilize placeholders that will be filled with customer data. For example, when {name} is used in an email template, it will be replaced with the buyer's name for the final email. This mechanism contained a security-relevant bug:

It was possible to exfiltrate information about the pretix system through specially crafted placeholder names such as {{event.init.code.cofilename}}. This way, an attacker with the ability to control email templates (usually every user of the pretix backend) could retrieve sensitive information from the system configuration, including even database passwords or API keys. pretix does include mechanisms to prevent the usage of such malicious placeholders, however due to a mistake in the code, they were not fully effective for this plugin.

Out of caution, we recommend that you rotate all passwords and API keys contained in your pretix.cfg https://docs.pretix.eu/self-hosting/config/  file.

Emails sent by pretix can utilize placeholders that will be filled with customer data. For example, when {name} is used in an email template, it will be replaced with the buyer's name for the final email. This mechanism contained a security-relevant bug:

It was possible to exfiltrate information about the pretix system through specially crafted placeholder names such as {{event.init.code.cofilename}}. This way, an attacker with the ability to control email templates (usually every user of the pretix backend) could retrieve sensitive information from the system configuration, including even database passwords or API keys. pretix does include mechanisms to prevent the usage of such malicious placeholders, however due to a mistake in the code, they were not fully effective for this plugin.

Out of caution, we recommend that you rotate all passwords and API keys contained in your pretix.cfg file.

Emails sent by pretix can utilize placeholders that will be filled with customer data. For example, when {name} is used in an email template, it will be replaced with the buyer's name for the final email. This mechanism contained two security-relevant bugs:

It was possible to exfiltrate information about the pretix system through specially crafted placeholder names such as {{event.init.code.cofilename}}. This way, an attacker with the ability to control email templates (usually every user of the pretix backend) could retrieve sensitive information from the system configuration, including even database passwords or API keys. pretix does include mechanisms to prevent the usage of such malicious placeholders, however due to a mistake in the code, they were not fully effective for the email subject.

Placeholders in subjects and plain text bodies of emails were wrongfully evaluated twice. Therefore, if the first evaluation of a placeholder again contains a placeholder, this second placeholder was rendered. This allows the rendering of placeholders controlled by the ticket buyer, and therefore the exploitation of the first issue as a ticket buyer. Luckily, the only buyer-controlled placeholder available in pretix by default (that is not validated in a way that prevents the issue) is {invoicecompany}, which is very unusual (but not impossible) to be contained in an email subject template. In addition to broadening the attack surface of the first issue, this could theoretically also leak information about an order to one of the attendees within that order. However, we also consider this scenario very unlikely under typical conditions.

Out of caution, we recommend that you rotate all passwords and API keys contained in your pretix.cfg https://docs.pretix.eu/self-hosting/config/  file.

Emails sent by pretix can utilize placeholders that will be filled with customer data. For example, when {name} is used in an email template, it will be replaced with the buyer's name for the final email. If the name of the attendee contained HTML or Markdown formatting, this was rendered as HTML in the resulting email. This way, a user could inject links or other formatted text through a maliciously formatted name. Since pretix applies a strict allow list approach to allowed HTML tags, this could not be abused for XSS or similarly dangerous attack chains. However, it can be used to manipulate emails in a way that makes user-provided content appear in a trustworthy and credible way, which can be abused for phishing.

Local File Inclusion vulnerability in pretix Widget WordPress plugin pretix-widget on Windows allows PHP Local File Inclusion. This issue affects pretix Widget WordPress plugin: from 1.0.0 through 1.0.5.

Stored XSS in organizer and event settings of pretix up to 2024.7.0 allows malicious event organizers to inject HTML tags into e-mail previews on settings page. The default Content Security Policy of pretix prevents execution of attacker-provided scripts, making exploitation unlikely. However, combined with a CSP bypass (which is not currently known) the vulnerability could be used to impersonate other organizers or staff users.

pretix before 2024.1.1 mishandles file validation.