navigator.userAgent not farbled properly in dynamic iframes

[pilgrim-brave]

See third-party test page here: https://arkenfox.github.io/TZP/tzp.html

With "aggressively block fingerprinting" setting, spaces are pseudo-randomly added to navigator.userAgent. Some dynamically created iframes are producing a hash that matches the unfarbled navigator.userAgent, suggesting that farbling is not happening in those iframes.

[pilgrim-brave]

STR:

Control:

• visit https://arkenfox.github.io/TZP/tzp.html#useragent
• verify Shields are up (default) and set to "block fingerprinting" (default)
• note value next to hash field in table
• next to "iframes" click "show" to reveal 7 more hash values
• all 8 hash values should match

Test:

• change Shields to "aggressively block fingerprinting"
• note value next to hash field in table
• next to "iframes" click "show" to reveal 7 more hash values
• all 8 hash values should match

[kjozwiak]

STR:

Control:

• visit https://arkenfox.github.io/TZP/tzp.html#useragent
• verify Shields are up (default) and set to "block fingerprinting" (default)
• note value next to hash field in table
• next to "iframes" click "show" to reveal 7 more hash values
• all 8 hash values should match

Test:

• change Shields to "aggressively block fingerprinting"
• note value next to hash field in table
• next to "iframes" click "show" to reveal 7 more hash values
• all 8 hash values should match

Thanks @pilgrim-brave 👍 @brave/qa-team example of the verification can also be seen via brave/brave-core#15917 (comment). You'll notice that the hashes under https://arkenfox.github.io/TZP/tzp.html#useragent are not matching with affected builds when FP is set as Strict.

[kjozwiak]

The above requires 1.46.138 or higher for 1.46.x verification 👍

[kjozwiak]

Verification PASSED on Pixel 6 running Android 13 using the following build(s):

Brave | 1.46.138 Chromium: 108.0.5359.94 (Official Build) (32-bit)
--- | ---
Revision | 713576b895246504ccc6b92c2fb8ce2d60194074-refs/branch-heads/5359_71@{#3}
OS | Android 13; Build/TQ1A.221205.011

Using the STR/Cases outlined via #26700 (comment), went through the following:

FP set as Standard

Example	Example

FP set as Strict

Example	Example

---

Verification PASSED on Samsung Galaxy Tab S8 Ultra running Android 13 using the following build(s):

Brave | 1.46.138 Chromium: 108.0.5359.94 (Official Build) (32-bit)
--- | ---
Revision | 713576b895246504ccc6b92c2fb8ce2d60194074-refs/branch-heads/5359_71@{#3}
OS | Android 13; Build/TP1A.220624.014

Using the STR/Cases outlined via #26700 (comment), went through the following:

FP set as Standard

FP set as Strict

[LaurenWags]

Verified with

Brave | 1.46.138 Chromium: 108.0.5359.94 (Official Build) (x86_64)
-- | --
Revision | 713576b895246504ccc6b92c2fb8ce2d60194074-refs/branch-heads/5359_71@{#3}
OS | macOS Version 12.6.1 (Build 21G217)

Went through the STR/Cases outlined via #26700 (comment) and ensured that the hashes under https://arkenfox.github.io/TZP/tzp.html#useragent are matching once FP is set as Strict/Aggressive as per the following:

1.46.134 Chromium: 108.0.5359.94 (without fix)	1.46.138 Chromium: 108.0.5359.94 (with fix)

Note that once FP is set as Strict/Aggressive, the hashes under https://arkenfox.github.io/TZP/tzp.html#useragent are not matching with 1.46.134 Chromium: 108.0.5359.94 which doesn't have the fix but matches with 1.46.138 Chromium: 108.0.5359.94 which has the fix. As per brave/brave-core#15917 (comment), we don't need to worry about the Spaces.

[btlechowski]

Verification passed on

Brave	1.46.138 Chromium: 108.0.5359.94 (Official Build) (64-bit)
Revision	713576b895246504ccc6b92c2fb8ce2d60194074-refs/branch-heads/5359_71@{#3}
OS	Ubuntu 18.04 LTS

Using the STR/Cases outlined via #26700 (comment), went through the following:

FP set as Standard

FP set as Aggressive

[MadhaviSeelam]

Verification PASSED using

Brave | 1.48.32 Chromium: 108.0.5359.94 (Official Build) nightly (64-bit)
-- | --
Revision | 713576b895246504ccc6b92c2fb8ce2d60194074-refs/branch-heads/5359_71@{#3}
OS | Windows 11 Version 21H2 (Build 22000.1219)

Verified using STR from #26700 (comment) and ensured that the hashes under https://arkenfox.github.io/TZP/tzp.html#useragent are matching once FP is set as Strict/Aggressive as per the following:

FP set as Standard

hash	iframes

FP set as Aggressive

hash	iframes