[Security] 9.3.0 release notes

[natasha-moore-elastic]

Summary

Resolves #4502: adds the 9.3.0 Security and Endpoint release notes.

Preview

Elastic Security release notes > 9.3.0

Elastic Security deprecations > 9.3.0

Generative AI disclosure

1. Did you use a generative AI (GenAI) tool to assist in creating this contribution?

• Yes
• No

Tool(s) and model(s) used:
Cursor, claude-4.5-opus-high

[github-actions]

Vale Linting Results

Summary: 1 suggestion found

💡 Suggestions (1)

File	Line	Rule	Message
release-notes/elastic-security/index.md	59	Elastic.WordChoice	Consider using 'deactivate, deselect, hide, turn off' instead of 'disable', unless the term is in the UI.

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[github-actions]

🔍 Preview links for changed docs

• release-notes/elastic-security/deprecations.md
• release-notes/elastic-security/index.md

[banderror]

@natasha-moore-elastic Thanks for the PR, it looks good 👍 I left a few minor comments.

[PhilippeOberti]

Features and bugs LGTM for the @elastic/security-threat-hunting-investigations team

[AsuNa-jp]

@natasha-moore-elastic
Thank you for putting together the release notes. I reviewed the sections relevant to me and the Endpoint Protections Team, and I left a few minor comments 🙇‍♀️

[nastasha-solomon]

thank you!