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GHSA-3xc2-h5r3-wv3r

MediumCVSS 5.7 / 10
Published May 5, 2026·Last modified May 14, 2026
Affected Components(0)

No affected components available

Description

Summary

Any ROLE_USER can create a tag with a formula string as its name (e.g. =SUM(54+51)) via POST /api/tags and assign it to a timesheet. When an admin exports timesheets to XLSX, ArrayFormatter.formatValue() joins tag names with implode() and returns the result unchanged. OpenSpout promotes any =-prefixed string to a FormulaCell, writing <f>SUM(54+51)</f> into the XLSX archive. Excel evaluates the formula when the file is opened.

Details

1. ArrayFormatter does not sanitize before returning

sanitizeDDE() exists on StringHelper and is called by TextFormatter, but ArrayFormatter never calls it.

// src/Export/Package/CellFormatter/ArrayFormatter.php:24
return implode(', ', $value);  // no sanitizeDDE() call

2. Tag name validation does not block formula trigger characters

The API blocks commas in tag names but permits =, +, -, and @ - all valid formula prefixes in Excel and LibreOffice Calc.

3. OpenSpout silently promotes strings to formula cells

Cell::fromValue("=SUM(54+51)") returns a FormulaCell with no warning.

PoC

  1. It logs in as normal user, creates tag =SUM(54+51), assigns it to a timesheet.
  2. Admin has to export timesheets to Excel version via /en/export/ endpoint.
<img width="1339" height="700" alt="image" src="https://github.com/user-attachments/assets/884c7943-5e3b-4647-8bcc-e264d6719d66" /> <img width="1304" height="128" alt="formula_injection_tags" src="https://github.com/user-attachments/assets/ef28f2ad-7491-4a15-bb18-1fcd6ff5e55a" />

Impact

  • Any ROLE_USER can plant a formula that executes on the workstation of any user who exports and opens timesheet data
  • A single malicious tag poisons all future exports across all users and date ranges until the tag is deleted

Fixes

  1. Prevent = being part of the tag name (and other fields as well)
  2. Use OpenSpout TextCell for everything that is a string
Risk Scores
Base Score
5.7

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. The attacker needs the user to perform some action, like clicking a link. The impact is confined to the system where the vulnerability exists. There is a high impact on the integrity of the data.

Threat Intelligence
5.2

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
0.22%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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