XSS sidekiq-unique-jobs UI server vulnerability
### Summary
Cross site scripting (XSS) potentially exposing cookies / sessions / localStorage, fixed by `sidekiq-unique-jobs` v8.0.7.
Specifically, this is a Reflected (Server-Side), Non-Self, Cross Site Scripting vulnerability, considered a **_P3_** on the BugCrowd taxonomy
https://bugcrowd.com/vulnerability-rating-taxonomy with the following categorization:
Cross-Site Scripting (XSS) > Reflected > Non-Self
It was initially thought there was a second vulnerability (RCE), but it was a false alarm. Injection is impossible with Redis:
> String escaping and NoSQL injection
> The Redis protocol has no concept of string escaping, so injection is impossible under normal circumstances using a normal client library. The protocol uses prefixed-length strings and is completely binary safe.
Ref:
https://redis.io/docs/management/security/
**XSS Vulnerability**
Specially crafted `GET` request parameters handled by any of the following endpoints of `sidekiq-unique-jobs`' "admin" web UI, allow a super-user attacker, or an unwitting, but authorized, victim, who has received a disguised / crafted link, to successfully execute malicious code, which could potentially steal cookies, session data, or local storage data from the app the `sidekiq-unique-jobs` web UI is mounted in.
1. `/changelogs`
2. `/locks`
3. `/expiring_locks`
This means if your `sidekiq-unique-jobs` web UI is mounted at `/sidekiq`, the vulnerable paths are:
1. `/sidekiq/changelogs`
2. `/sidekiq/locks`
3. `/sidekiq/expiring_locks`
XSS vulnerability is an instance of CAPEC-32: XSS Through HTTP Query Strings
https://capec.mitre.org/data/definitions/32.html, which is related to CWE-80
https://cwe.mitre.org/data/definitions/80.html. In certain cases where it results in a server error with status 500, it could be considered a vector for uncontrolled resource consumption, given that errors can be much more resource intensive that normal requests, and thus CWE-400
https://cwe.mitre.org/data/definitions/400.html & CWE-754
https://cwe.mitre.org/data/definitions/754.html may also be relevant.
### Details
Fix for the XSS vulnerability was released in `sidekiq-unique-jobs` v8.0.7
https://github.com/mhenrixon/sidekiq-unique-jobs/releases/tag/v8.0.7.
This is an analogous attack vector to that which affected `sidekiq` gem from version v7.0.4 to v7.0.7, and was given identifiers GHSA-h3r8-h5qw-4r35
https://github.com/advisories/GHSA-h3r8-h5qw-4r35 & CVE-2023-1892
https://github.com/advisories/GHSA-h3r8-h5qw-4r35.
The vulnerability in `sidekiq-unique-jobs`' was *not* fixed by `sidekiq` v7.0.8
https://github.com/sidekiq/sidekiq/blob/main/Changes.md#708, nor the more recent `sidekiq` v7.2.0
https://github.com/sidekiq/sidekiq/blob/main/Changes.md#720 releases; they are similar but unrelated, distinct vulnerabilities in adjacent projects.
Note #1: The admin web UI for `sidekiq-unique-jobs` is not protected by any authorization constraint in the default configuration. Auth constraints must be configured by the programmer. It is recommended and expected that users will configure authorization constrains on the "admin" UI. This is not specifically related to the vulnerability but may make users who fail to constrain their "admin" UI even more vulnerable.
Note #2: Most users of the library will not have configured the UI on a sandboxed subdomain, making all their cookies, localStorage data and session secrets vulnerable to exposure
https://liveoverflow.com/do-not-use-alert-1-in-xss/. The purpose of a sandboxed subdomain is expressly to prevent leaking sensitive data through XSS attacks.
XSS Fix PR:
https://github.com/mhenrixon/sidekiq-unique-jobs/pull/829
### PoC
**XSS**
Use a string like:
```
%22%3E%3Cimg/src/onerror=alert(document.domain)%3E
```
as the value for one of the parameters that are handled without escaping.
Reference:
https://liveoverflow.com/do-not-use-alert-1-in-xss/
1. Visit /sidekiq/changelogs
http://localhost:3000/sidekiq/changelogs - with a crafted query string like one of the following:
a. Screenshot: !XSS changelogs sidekiq-unique-jobs lte v8 0 6
https://github.com/mhenrixon/sidekiq-unique-jobs/assets/19505/61788878-96af-4f97-8c11-b4c343b30c89
b. `filter` is XSS vulnerable: `?filter=%22%3E%3Cimg/src/onerror=alert(document.domain)%3E`
c. `count` is vulnerable to triggering an application error (status 500), potentially allowing resource exhaustion `?count=%22%3E%3Cimg/src/onerror=alert(document.domain)%3E`
1. Screenshot: !1c changelogs count
https://github.com/mhenrixon/sidekiq-unique-jobs/assets/19505/4c2cfe41-b8f5-49ef-90eb-4a20841874f9
2. Visit /sidekiq/locks
http://localhost:3000/sidekiq/locks - with a crafted query string like one of the following:
a. Screenshot: !XSS locks sidekiq-unique-jobs lte v8 0 6
https://github.com/mhenrixon/sidekiq-unique-jobs/assets/19505/4a60cf44-8caa-42a3-a812-3ace81c21e0c
b. `filter` is XSS vulnerable: `?filter=%22%3E%3Cimg/src/onerror=alert(document.domain)%3E`
c. `count` is vulnerable to triggering an application error (status 500), potentially allowing resource exhaustion `?count=%22%3E%3Cimg/src/onerror=alert(document.domain)%3E`
1. Screenshot: !2c locks count
https://github.com/mhenrixon/sidekiq-unique-jobs/assets/19505/630d98a6-a3b4-46c8-b7a4-ca8c0e306c13
3. Visit /sidekiq/expiring_locks
http://localhost:3000/sidekiq/expiring_locks - with a crafted query string like one of the following:
a. Screenshot: !XSS expiring_locks sidekiq-unique-jobs lte v8 0 6
https://github.com/mhenrixon/sidekiq-unique-jobs/assets/19505/7566515e-1edb-4436-8ec4-672c28437534
b. `filter` is XSS vulnerable: `?filter=%22%3E%3Cimg/src/onerror=alert(document.domain)%3E`
### Impact
This is a vulnerability of critical severity, which impacts many thousands of sites, since `sidekiq-unique-jobs` is widely deployed across the industry, with multiple attack vectors.