Shields should be robust against invalid CSS in stylesheet injections

[antonok-edm]

A recent change to uBO filter lists resulted in the following two cosmetic filters being shipped out to Brave users:

##html[lang] > body#body > head\" > div.cv-xwrapper > div.cvc > div.cv-inner
##html[lang] > body#body > head\" > div.cvh.BlockClicksActivityBusy

Users who received those rules faced some issues with cosmetic filtering, due to errors thrown by Brave's injected content script. The issue was ultimately resolved by a serverside patch to remove the problematic rules.

An error was shown in the console for affected users:

Uncaught DOMException: Failed to execute 'insertRule' on 'CSSStyleSheet': Failed to parse the rule '##html[lang] > body#body > head\" > div.cv-xwrapper > div.cvc > div.cv-inner{display:none !important;}'

That error ultimately traces to this insertRule call. It turns out that invalid CSS injected here can abort the rest of the injections.

We should add a try/catch block around the injection to improve robustness against invalid data.

[antonok-edm]

see also #40151 (comment)

[LaurenWags]

Verified with

Brave | 1.70.95 Chromium: 128.0.6613.114 (Official Build) beta (x86_64)
-- | --
Revision | 58a39a29fce4db0417a269766b0157fad397767b
OS | macOS Version 13.6.9 (Build 22G830)

Verified test plan from brave/brave-core#25015.
Confirmed no messages in the console about Uncaught DOMException: Failed to execute 'insertRule' on 'CSSStyleSheet'.

Example	Example

[LaurenWags]

@brave/qa-team use the test plan under brave/brave-core#25015 for verifying this issue 👍🏻

[GeetaSarvadnya]

Verification PASSED on

Brave | 1.70.94 Chromium: 128.0.6613.114 (Official Build) beta (64-bit)
-- | --
Revision | 7ee7ec28264896bd8a9aff39cdb9432da38be028
OS | Windows 10 Version 22H2 (Build 19045.4780)

Verified test plan from brave/brave-core#25015.
Confirmed no messages in the console about Uncaught DOMException: Failed to execute 'insertRule' on 'CSSStyleSheet'.

Example	Example

[hffvld]

This issue also affects Android devices, but because we don't have access to Profile folder on our test devices, we're unable to verify it right now.

[GeetaSarvadnya]

Verification PASSED on

Brave	1.70.110 Chromium: 128.0.6613.138 (Official Build) beta (64-bit) 
Revision	7dec99ca278e09ce2087e9f04914f0aa2507ea4c
OS	Linux

Verified test plan from brave/brave-core#25015.
Confirmed no messages in the console about Uncaught DOMException: Failed to execute 'insertRule' on 'CSSStyleSheet'.

Example	Example

[hffvld]

Verified on rooted Pixel 6 using version(s):

Device/OS: Pixel 6 / oriole-user 14 AP2A.240905.003.F1 release-keys
Brave build: 1.70.114
Chromium: 129.0.6668.42 (Official Build) (64-bit)

---

STEPS:

1. Follow the steps from Update adblock-rust to v0.8.12 brave-core#25015 (comment)
2. Verify

ACTUAL RESULTS:

• Verified that no messages in the console about Uncaught DOMException: Failed to execute 'insertRule' on 'CSSStyleSheet'.

---

1	2	3