macOS/iOS: DuckDuckGo search very slow to load, high CPU usage

[fnschmidt]

Please answer the following questions for yourself before submitting an issue.

• I am running the latest version
• I made sure all content blockers are enabled in Safari settings
• I checked the documentation and found no answer
• I checked to make sure that this issue has not already been filed

AdGuard version

1.1.20 (or 4.5.8 on iOS)

Environment

- OS: Sequoia 15.3.1
- Safari version: 18.3 (20620.2.4.11.5)

What filters do you have enabled?

AdGuard Base filter, AdGuard Tracking Protection filter

Issue Details

Steps to reproduce:

1. enable the filters
2. Navigate to https://duckduckgo.com/?q=test

Expected Behavior

DDG search results load as fast as when using Google or loading any other website, even with AdGuard enabled.

Actual Behavior

Whenever DDG is used for a search, a 4-5 second pause occurs. Safari Web Content uses 100% of a CPU core during this time (on an M1 Pro)

Screenshots

Screen recording

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Additional Information

• this issue occurs on both macOS and iOS, where it started to occur perhaps in november or december 2024. This did not start after an iOS or Safari update. There were a few days before both my iOS device and macOS was affected, perhaps because the filter lists were updated at different points
• only the search results page is affected, duckduckgo.com without query is fine
• Using the page search box also takes multiple seconds
• Reloading the page is also slow