fix: preserve RAG/STT config and block unsafe iframe sources

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• Description: Provide a concise description of the changes made in this pull request.
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Changelog Entry

Description

• Fixes critical regressions where partial RAG config updates could persistently clear upload limits, image compression settings, and the reranking model; blank STT MIME settings could disable transcription instance-wide; and generic markdown iframes could load same-origin or unsafe URLs with user credentials.

Added

• Focused regression coverage for config helper behavior and iframe source validation.

Changed

• Normalizes configured STT supported content types before saving or matching them.
• Validates generic iframe sources through a shared helper before rendering.

Deprecated

• None.

Removed

• None.

Fixed

• Preserves existing RAG upload limit, image compression, and reranking settings when partial /api/v1/retrieval/config/update payloads omit those fields.
• Filters blank STT MIME entries so a default blank admin field does not store [''] and block all audio/video transcription.
• Rejects relative, same-origin, javascript:, data:, and other non-HTTP(S) generic iframe sources in markdown rendering.

Security

• Prevents authenticated same-origin GETs from being triggered by chat-rendered generic iframes such as /api/v1/auths/signout.
• Prevents missing upload limits from being silently persisted by unrelated RAG config saves.

Breaking Changes

• BREAKING CHANGE: None.

---

Additional Information

Bug and impact:

• Admin web-search saves sent partial RAG config payloads; omitted file/reranking fields were stored as None, removing upload limits and corrupting RAG settings across restarts.
• Saving Audio settings with a blank supported-MIME field stored [''], making STT MIME fallback unreachable and rejecting all transcription uploads.
• Generic iframe rendering accepted raw markdown src values, allowing chat content to load credentialed same-origin endpoints.

Root cause:

• Newly optional config fields were assigned directly instead of preserving existing values on partial updates.
• STT content-type lists were not normalized on admin update or runtime matching.
• Generic iframe rendering parsed src from unsanitized token text with no URL policy.

Fix:

• Added small config helpers for preserving omitted values and normalizing STT MIME lists, then used them in RAG, audio, and upload processing paths.
• Added a shared iframe source validator and regression tests.

Validation performed:

• python3 -m pytest tests/test_config_helpers.py attempted, but pytest is not installed in the base image.
• Manual execution of all tests/test_config_helpers.py test functions: passed.
• python3 -m py_compile backend/open_webui/utils/config_helpers.py backend/open_webui/routers/audio.py backend/open_webui/routers/files.py backend/open_webui/routers/retrieval.py: passed.
• npm ci: passed.
• npx vitest run src/lib/utils/iframe.test.ts: passed (3 tests).
• npx prettier --check src/lib/utils/iframe.ts src/lib/utils/iframe.test.ts src/lib/components/chat/Messages/Markdown/HTMLToken.svelte: passed; Prettier emitted existing pluginSearchDirs option warnings.
• git diff --check origin/main..HEAD: passed.

Screenshots or Videos

• Not applicable.

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