Email security gateways (Microsoft Defender Safe Links / ATP, Proofpoint,
Mimecast, Barracuda, etc.) auto-fetch and often render every link in a
campaign email to scan for malware. The advanced ones drive a real headless
browser, execute JS, and fire Umami pageviews/clicks that masquerade as human
visits -- inflating campaign click-through.
New site/public/js/pw-bot-filter.js queries multiple real-browser signals and
gates Umami via its official data-before-send hook (umamiBeforeSend), dropping
all events when the visitor is a bot. Signals (from empirical chromium probing):
decisive: navigator.webdriver, HeadlessChrome UA, known scanner UAs, zero/
collapsed screen|viewport|outer geometry, window LARGER than the
physical screen (impossible on real HW; uses outerW/H so page zoom
does not false-positive), software GPU rasterizer (SwiftShader/
llvmpipe/swrast via WebGL UNMASKED_RENDERER), zero logical CPUs.
soft (>=2 to trip): tiny screen, inner>screen, low color depth, empty
navigator.languages, no input device (no fine/coarse pointer + no
hover + 0 touch), no WebGL on a desktop UA.
Designed to FAIL OPEN: only strong/corroborated evidence suppresses, so real
visitors (incl. zoomed, privacy-tooled, remote-desktop, kiosk) still count.
Wired before the Umami tag in Base.astro (Astro pages) and all 86 static
public/**/*.html pages; both load with defer so order is guaranteed and the
hook is defined before Umami reads it.
Tested end-to-end with chromium (site/tests/bot-filter.test.sh, 4/4):
default headless-new, spoofed-Windows-UA + normal 1366x768 window, and
spoofed-UA + 1x1 window are all caught; hook returns null to drop the event.
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