Timestamp is embedded in extension manifest files
Inspecting two Fenix .apk files one can see:
diff -r 1/test/assets/extensions/ads/manifest.json
2/test/assets/extensions/ads/manifest.json
9c9
< "version": "57.0.0.0910095351",
---
> "version": "57.0.0.0910102701",
diff -r 1/test/assets/extensions/cookies/manifest.json
2/test/assets/extensions/cookies/manifest.json
9c9
< "version": "57.0.0.0910095351",
---
> "version": "57.0.0.0910102701",The versions stem from a respective manifest.template.json which gets
processed in app/build.gradle like
def values = ['version': AndroidComponents.VERSION + "." + new
Date().format('MMddHHmmss')]