Package Instance

TYPO3 CMS Possible Insecure Deserialization in Extbase Request Handling
It has been discovered that request handling in Extbase can be vulnerable to insecure deserialization. User submitted payload has to be signed with a corresponding HMAC-SHA1 using the sensitive TYPO3 encryptionKey as secret - invalid or unsigned payload is not deserialized.

However, since sensitive information could have been leaked by accident (e.g. in repositories or in commonly known and unprotected backup files), there is the possibility that attackers know the private encryptionKey and are able to calculate the required HMAC-SHA1 to allow a malicious payload to be deserialized.

Requirements for successfully exploiting this vulnerability (all of the following):

- rendering at least one Extbase plugin in the frontend
- encryptionKey has been leaked (from LocalConfiguration.php or corresponding .env file)

Insecure Deserialization in TYPO3 CMS
It has been discovered that the Form Framework (system extension "form") is vulnerable to Insecure Deserialization when being used with the additional PHP PECL package “yaml”, which is capable of unserializing YAML contents to PHP objects. A valid backend user account as well as having PHP setting "yaml.decode_php" enabled is needed to exploit this vulnerability (which is the default value according to PHP documentation).

TYPO3 Cross-Site Scripting in Link Handling
It has been discovered that `t3://` URL handling and typolink functionality are vulnerable to cross-site scripting. Not only regular backend forms are affected but also frontend extensions which use the rendering with typolink.

Improper Authentication
Authentication Bypass in TYPO3 CMS.

Backend Same-Site Request Forgery in TYPO3 CMS
> ### Meta
> * CVSS v3.1: AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C
> * CWE-352
> * CWE-346

### Problem
It has been discovered that backend user interface and install tool are vulnerable to same-origin request forgery. A backend user can be tricked into interacting with a malicious resource an attacker previously managed to upload to the web server - scripts are then executed with the privileges of the victims' user session.

In a worst case scenario new admin users can be created which can directly be used by an attacker. The vulnerability is basically a cross-site request forgery (CSRF) triggered by a cross-site scripting vulnerability (XSS) - but happens on the same target host - thus, it’s actually a same-origin request forgery.

Malicious payload such as HTML containing JavaScript might be provided by either an authenticated backend user or by a non-authenticated user using a 3rd party extension - e.g. file upload in a contact form with knowing the target location.

The attacked victim requires an active and valid backend or install tool user sessions at the time of the attack to be successful.

### Solution
Update to TYPO3 versions 9.5.17 or 10.4.2 that mitigates the problem described.

### Additional Considerations

The deployment of additional mitigation techniques is suggested as described below.

#### Sudo Mode Extension

This TYPO3 extension intercepts modifications to security relevant database tables, e.g. those storing user accounts or storages of the file abstraction layer. Modifications need to confirmed by again by the acting user with providing their password again - this technique is known as "sudo mode". This way unintended actions happening in the background can be mitigated.

* https://github.com/FriendsOfTYPO3/sudo-mode
* https://extensions.typo3.org/extension/sudo_mode

#### Content Security Policy

[Content Security Policies](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy) tell (modern) browsers how resources served a particular site are handled - it also it possible to disallow script executions for specific locations. In a TYPO3 context it is suggested to disallow direct script execution at least for locations `/fileadmin/` and `/uploads/`.

```
# in fileadmin/.htaccess
<IfModule mod_headers.c>
	Header add Content-Security-Policy "default-src 'self'; script-src 'none';"
</IfModule>
```

### Credits
Thanks to Matteo Bonaker who reported this issue and to TYPO3 security team member Oliver Hader who fixed the issue.

### References
* https://typo3.org/security/advisory/typo3-core-sa-2020-006

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
In Bootstrap, XSS is possible in the data-target property of scrollspy.

TYPO3  SQL Injection in low-level Query Generator
An issue was discovered in TYPO3 before 8.7.30, 9.x before 9.5.12, and 10.x before 10.2.2. Because escaping of user-submitted content is mishandled, the class QueryGenerator is vulnerable to SQL injection. Exploitation requires having the system extension ext:lowlevel installed, and a valid backend user who has administrator privileges.